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Septic Mound Systems

1. 132 3s 39 55 3m 1 6 36 373 46 50 525 57 60 m s 4 o amp 72 50 WA DOH Publication 337 009 Page 46 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 1 Lateral Design Table continued Orifice Spacing Pipe Material Class 200 Class 160 1 6 9 30 is 465 54 56 625 65 72 75 ss ss 53 1s 3 10 105 ur 15 p 4o m asd s 69 m 2 2 T m 23 3s 95 925 95 m 23 3 s 108 um 132 5m 2 3 150 5m 168 as e ee a WE NE db ue 1 1 s 225 MEL E dI E EE HE 3 5 j4 1 is 2 315 aus 2 3 3 3s j 15 25 95 43 is WE gt gt z a is Ua 56 60 65 70 w os e 6 7 78 39 39 Ua 46 is 525 55 WA DOH Publication 337 009 Page 47 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 1 Lateral Design Table continued Maximum Lateral Length ft Orifice Lateral Orifice Spacing Pipe Material feet Schedule 40 Class200 Class 160 por rH 3 54 60 63 4 64 72 76 1 4 5 7
2. AM NEAN REN BE ni 216 50 09 1 16 o 44 09 7 p E 194 17 18 o 09 Combine with Table X 2 to Make One Table 12 02 Pumps HYDRAULICS X 34 SUMMARY Pumping stations may be required to overcome site obstacles When pumping stations are needed they must be carefully selected and designed to create a good working system The pumping stations must be watertight and not subject to corrosion The selection of the right pump based on the pump type and the pump characteristics can be time consuming but is critical to the proper operation of the system Pumping stations must be accessible to allow for service and maintenance on the pumps 12 02 Pumps HYDRAULICS X 35 REFERENCES AND READING MATERIALS Iowa DNR Onsite Sewage Design and Reference Manual Section E Pressure Distribution and Pumping Systems Iowa Department of Natural Resources 2003 www iowadnr com water septic manual html www iowadnr com water septic manual html Jones D D J E Yahner and E R Miller Steps in Constructing a Mound Bed Type Septic System ID 163 Purdue University Cooperative Extension Service April 1990 www ces purdue edu extmedia ID ID 163 html Kang Y W K Mancl and R Gustafson Pressure Distribution of Wastewater Design and Construction in Ohio Bulletin 829 The Ohio State Universis Cooperative Extension http ohioline osu edu b829 index htm
3. 31 3 6 Findingsand 31 jl 32 Appendix A Useful Tables for Pressure Distribution e 43 Appendix B Volume of PIpe ci escono mer ERE REL EEDUERS ERE HEN SUED sisas TUE 57 Appendix C Advantages Disadvantages of Dosing Systems c ceeeeeeeeeee 58 Appendix D Advantages Disadvantages of Siphon Dosed Systems 60 Appendix E Mee Pro 61 Glossary of Terms http www doh wa gov ehp ts WW RSG Glossary 8 29 07 pdf WA DOH Publication 337 009 Page 5 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Preface The recommended standards contained in this document have been developed for statewide application Regional differences may however result in application of this technology in a manner different than it is presented here In some localities greater allowances than those described here may reasonably be granted In other localities allowances that are provided for in this document may be restricted In either setting the local health officer has full authority in the application of this technology consistent with Chapter 246 272A
4. Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 a An alternate method to the squirt height is to attach a clear PVC stand pipe to the end of the lateral The true residual head is measured from the top of the lateral pipe to the top of the water column Q Check float placement High water alarm on level off level and redundant off alarm must activate or deactivate at the elevation called out on the plan It is recommended that for simplicity and accuracy these adjustments be made with the float tree out of the water Ensure that the pump delivers the correct dose to the drainfield Demand dose systems Verify that dry float settings completed above send the correct dose to the drainfield when floats are in water This may require minor adjustments of float placement Timed dose systems 1 Determine the time required to send a full dose to the drainfield This can be done by running the system in manual Be sure there is plenty of water in the pump chamber Timer run times provided by designers or engineers must be field tested 2 Using the time obtained above verify that when the system runs automatically it runs the time required to send the proper dose to the drainfield This is important because timers are difficult to set i e setting a timer to 2 2 minutes may not ensure a run time of 2 2 minutes Two steps to speed this process a
5. 1 3 Q 0 4145 The total head is the sum of the elevation force main and network heads f The total head is the sum of the elevation force main and network heads Note Orifice is synonymous with perforation 2 Determine the force main diameter Force main diameter 3 determined in Step 10 of Distribution Network Design 3 Select the pressurization unit Plot the performance curves of several effluent pumps and the system performance curve For the system curve plot the flow rates versus the total head On the system curve Figure X 14 place an X on the curve at the desired flow rate in this case 60 gpm Select the pump represented by the pump performance curve located next along the system performance curve just after 60 gpm Pump B as that is where the pump will operate Pump C could be used but it is over sized for the conditions 12 02 6 Pumps AnD HYDRAULICS X 26 30 25 SYSTEM CURVE Force main diameter 3 Force main length 125 ft Void volume 0 367 gal ft Net dose volume 5 6n ft x 0 163 gal ft 46 gallons per dose Flow Back from force main 125 ft x 0 367 gal ft 46 gallons Set the floats so that a total of 92 gallons will be dosed with 46 gallons flowing back into pump chamber to drain the pipe when the pump stops Size the dose chamber Based on the dose volume storage volume and room for a block beneath the pump and control space a 500 to 750 gallon chamber will su
6. MAX 8 1 2 S0IiL COVER RIGID PERFORATED PLASTIC PIPE 4 MiN FROM BOTTOM OF TRENCH TO WATER TABLE OR CLAY OR ROCK LAYER PUMPING STATION FOR HOMES PUMP IN BASEMENT Figure X 6 Pump Lifts Sewage to Shallow Septic Tank Placement for Easier and Much Less Costly Maintenance The pump tank must be accessible for maintenance A manhole with a minimum diameter of 24 inches must be provided into the pump tank The access opening into the tank itself must be a minimum of 20 inches A larger manhole is preferred and may be required depending on the type of pump used The manhole cover must have a lock mechanism to prevent unauthorized persons from opening the tank An unsecured manhole cover is a serious safety hazard and may become a target for vandalism The pumping station is a confined space and may contain 12 02 Pumps HYDRAULICS X 7 dangerous gases The manhole must provide access for maintenance and servicing the pump but in no case should the pump tank be entered unless all OSHA safety regulations regarding a confined space entry are observed The pump should be installed with a quick release discharge which is accessible at the top of the manhole This will allow the pump to be serviced or replaced as needed All electrical connections should be made outside the pump tank in approved waterproof connection boxes The pump station must have an electrical disconnect which is located outside the house and is acc
7. Recommended Standards and Guidance Effective Date July 1 2009 FINISHED GRADE TRANSPORT PIPE SECURED LID WITH GAS TIGHT SEAL 24 DIAMETER ACCESS FROM a VENT PIPE SEPTIC __ 5 1 TANK 7 p TRAP VENT ON i 24 TO OFF gt DRAINFIELD SECURE 25 GALLONS INCH 600 GALLONS DOSE MOUNTING N SIPHON TO TRANSPORT SIPHON TANK REDUCER HIGH DOSE VOLUME EXAMPLE SECURED LID WITH GAS TIGHT SEAL E 24 DIAMETER ACCESS RISER FINISHED GRADE e ES TRANSPORT PIPE VENT PIPE 5 TS TANK ON 1 12 orr TO DRAINFIELD 7 5 GALLONS INCH N SIPHON TO 90 GALLONS DOSE N DUCERE S SECURE MOUNTING SIPHON TANK LOW DOSE VOLUME EXAMPLE FIGURE 10 Page 42 of 61 WA DOH Publication 337 009 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Appendix A Useful Tables for Pressure Distribution The design tables in the four sections of this appendix have been developed in order to allow the designer to evaluate alternative lateral configurations Appendix A 1 LATERAL DESIGN TABLE has a table of maximum lateral lengths for various lateral diameters orifice diameters and orifice spacings and includes design criteria used to calculate maximum lateral lengths Appendix A 2 ORIFICE DISCHARGE RATE DESIGN AID contains a derivation of an equation used to c
8. ami _ The pump run iine should be determined with a stop watch The stop watch should also be used to measure the time interval between pump cycles This data should be recorded at the time that the system is placed into service and should be kept available at the site to aid in long term monitoring and maintenance The last test of the system is to determine the squirt height or residual head The minimum residual head should be between 2 5 feet The easiest method for measuring the residual head is to attach a clear pipe onto the end of the lateral and measure the static head which is the vertical distance between the lateral and the top of the liquid standing in the clear pipe 12 02 Pumps HYDRAULICS X 32 Maintenance As discussed earlier these systems will require maintenance The equipment must be checked on a regular schedule to be sure that screens in the tank or around the pump intake and the effluent filter are not clogged In addition the lateral lines should be flushed to dislodge any solids and remove the biological slime which develops in the pipes The laterals should be tested for residual pressure and for equal flow The pump run time and the number of cycles should be checked against the original design of the system The pump drawdown volume should also be checked periodically and may need to be adjusted with the timer in the control box Additional items to be checked in the septic tank or pump tank include checking for s
9. FILTER SEDIMENTS SEPTIC TANK TYPICAL SECURED LID WITH GAS TIGHT SEAL THREADED UNION 24 DIAMETER ACCESS RISER SERVICE X VALVE TO DRAINFIELD EMERGENCY STORAGE ANTI SIPHON VALVE INDEPENDENT FLOAT STEM FOR FLOAT MOUNTING CHECK VALVE WORKING VOLUME ENCLOSED PUMP SEDIMENT SHROUD SEDIMENTS SUBMERSIBLE CENTRIFUGAL PUMP PUMP CHAMBER TYPICAL AS NEEDED FIGURE 2 WA DOH Publication 337 009 Page 33 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 DOWN SLOPE f GRADIENT y FEATURES 1 FLOW IS CONTROLLED TO EACH LATERAL BY FLOW CONTROL VALVE 2 BACKFLOW IS PREVENTED BY CHECK VALVE ON EACH LATERAL FEEDER PIPE 3 PIPING ABOVE CHECK VALVES IS ALWAYS FLOODED LENGTH AND VOLUME OF LATERALS OR LATERAL FEEDER PIPES DOES NOT IMPACT SIZE OF DOSE LEGEND CHECK VALVE FLOW CONTROL x VALVE WA DOH Publication 337 009 PRESSURE DISTRIBUTION LATERALS LATERAL FEEDER PIPES LOCATE VALVE CONTROL BOX OQ T AT ELEVATION BELOW A LOWEST LATERAL SERVED HEADER MANIFOLD PIPE TRANSPORT PIPE FROM PUMP CHAMBER PRESSURE DISTRIBUTION DRAINFIELD SLOPING GROUND FIGURE 3A Page 34 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 PRESSURE DISTRIBUTION LATERALS TRANSPORT
10. Two laterals on each side of center feed 4 laterals spaced 2 ft apart 8 Calculate the manifold size The force main diameter is determined from Table A 2 on the manual The manifold is generally the same size as force main as it is an extension of the force main or it could be one size smaller This example will use a 2 manifold 9 Determine network discharge rate NDR NDR 4 laterals x 14 8 gpm lateral 59 2 or 60 gpm Pump has to discharge a minimum of 60 gpm against a total dynamic head yet to be determined 10 Total dynamic head Sum of the following System head 1 3 x distal head ft 1 3x 3 5 ft 4 5 ft Elevation head 9 0 ft Pump shut off to network elevation Head Loss in Force Main Table A 3 and A 4 for 60 gallons and 125 ft of force main and 3 elbows Equivalent length of pipe for fittings can be found in Table A 3 3 2 90 elbows 9 0 ft each 27 ft of pipe equivalent Head Loss through 100 of PVC pipe can be found in Table A 2 125 of 2 force main plus the head loss in the fittings equals 7 0 125 ft 27 ft 100 10 6 ft Total Dynamic Head TDH Sum of the three TDH System head Elevation head Head Loss in Force Main 4 5 9 10 6 24 1 ft 2 force main 24 ft of head 11 Pump Summary Pump must discharge 60 gpm against a head of 24 ft with 2 force main These are the calculated flow and head values The actual flow and head will be determined by the pump selected A system
11. a AR BR OO DIDI DIDI DI AID Oo 12 8 10 14 20 24 32 40 12 8 10 14 20 24 32 30 gt 00 00 00 00 N AJAJAJA Ay A A BLRIDID CO 0 CO DI NI A A oo NINJIN 4A 4A oo 0 0 8 10 8 10 8 10 10 8 10 gt gt 10 Table A 3 Friction Loss in Schedule 40 Plastic Pipe ft 100 ft Based on Hazan Williams C 150 Pipe Diameter Inches Flow 1 11 4 11 2 2 3 4 6 8 10 GPM 1 0 07 2 0 28 0 07 3 0 60 0 16 0 07 4 1 01 0 25 0 12 5 1 52 0 39 0 18 6 2 14 0 55 0 25 0 07 Velocities in this area are below 2 ft sec 7 2 89 0 76 0 36 0 10 8 3 63 0 97 0 46 0 14 9 4 57 1 21 0 58 0 17 0 5 50 1 46 0 70 0 21 1 1 77 0 84 0 25 2 2 09 1 01 0 30 3 2 42 1 17 0 35 4 2 74 1 33 0 39 5 3 06 1 45 0 44 0 07 6 3 49 1 65 0 50 0 08 7 3 93 1 86 0 56 0 09 8 4 37 2 07 0 62 0 10 9 4 81 228 0 68 0 11 20 5 23 2 46 0 74 0 12 25 3 75 1 10 0 16 30 5 22 1 54 0 23 35 2 05 0 30 0 07 40 2 62 0 39 0 09 45 3 27 0 48 0 12 50 3 98 0 58 0 16 60 0 81 0 21 70 1 06 0 28 80 1 38 0 37 90 1 73 0 46 100 2 09 0 55 0 07 150 1 17 0 16 200 0 28 0 07 250 0 41 0 11 300 0 58 0 16 350 0 78 0 20 0 07 400 0 99 0 26 0 09 450 1 22 0 32 0 11 500 0 38 0 14 600 0 54 0 18 700 0 72 0 24 800 0 32 900 0 38 1000 0 46 11 Table A 4 Friction lo
12. 12 02 Pumps HYDRAULICS X 15 SELECT THE PUMP FOR THE APPLICATION The pumps must be selected for the specific flow and head or pressure requirements not just on the basis of horsepower voltage or other factor Just because a pump worked well in one application does not mean it will work well in a different one With wastewater the presence of solids must be considered The three factors that determine the total dynamic head of a pump are elevation difference between the pump and point of discharge the pressure requirements of the operating system and the friction loss in the piping For the example in Figure X 11 11A assume that there is an elevation difference of 17 feet between the top of the pump and the manifold in the pressure distribution system When pumping to a pressure distribution system as in this example add five feet for pressure required at the manifold If pumping to a drop box gravity system then zero would be put in section B item 2 Table X 1 shows the friction loss for Schedule 40 PVC plastic pipe Friction loss Head Perforation Diameter inches 7 32 4 2 1 0 0 56 POINT OF Hi PIPE LENGTH 1 5 0 69 th A DISCHARGE 2 06 0 80 po 1 2 5 HL 3 0 tb 4 0 a ELEVATION e DISTANCE 5 0 CD a Use 1 0 foot of head b Use 2 0 feet of head for other establishments Friction loss depends on th
13. 32 SUMMARY X 34 REFERENCES AND ADDITIONAL READING MATERIALS X 35 TABLES X 1 Schedule 40 Plastic Pipe Friction Loss Diameters and Volume X 2 Orifice Discharge Rates in Gallons per Minute X 3 Friction Loss in PVC Plastic Pipe X 4 Head and Calculations for Various Operating Flow and Pressure X 5 Void Volume for Various Diameters of Schedule 40 Pipe X 6 Orifice Flow Rate gpm for Different Sizes and Operating Pressure FIGURES X 1 Pump Used to Lift Wastewater to a Higher Elevation that the Source X 2 Pump Discharge Delivery to a Gravity Distribution Lateral Drop Box X 3 Gravity Distribution Lateral Drop Box X 4 Gravity Serves Ground Floor and a Pump Lifts Sewage from Basement X 5 Pump Lifts Tank Effluent to a Shallow Absorption Field X 6 Pump Lifts Sewage to Shallow Septic Tank for Easy Access X 7 Section of Pump Tank Showing Pump Wiring and Float Locations X 8 Section of Pump Tank Showing Wiring and Electricity away from House X 9 Duplex Pump Station has Two Alternating Pumps X 10 Example Pump Curves for Four Pumps X 11 11A Example Problem Pump Placement X 12 Section of Low Pressure Pipe Lateral Indicating Holes for Drainage X 13 Graph of Lateral Length Orifice Spacing and Pipe Size X 14 Plotted System Operating Curve and Pump Curves to Select Pump X 15 Typical Pump Tank Controls and Pipe Network Components X 16 Supply Manifold and Connection to Low Pressure Lateral X 17 Detail of Turn up and Cleanout for Pr
14. Configuration of the network The configuration and size of the absorption field must meet all soil and site criteria Once any limitations have been established the distribution network can be designed 2 Determine the length of the laterals Lateral lengths are defined as the distance length from the manifold to the end of the lateral For a center manifold it is approximately one half the length of the absorption area For end manifolds it is approximately the length of the absorption area The lateral should end about 6 to 12 from the end of the absorption bed 3 Determine the perforation size spacing and position The size of the perforation or orifices spacing of the orifices and the number of orifices must be matched with the flow rate to the network Size The typical perforation diameter has been 1 4 but with the requirement of Class I effluent carry over particles have been greatly reduced allowing smaller diameter orifices to be used Orifices as small as 1 8 are commonly used in sand filter design however orifice shields are generally used to protect the orifice from being compromised by the aggregate Smaller diameter perforations are also at risk from burrs when drilling Shop drilling the orifices under tight specifications reduces the concern A sharp drill bit will drill a much more uniform orifice than a dull drill Replace drills often Remove all burrs and filing from pipe before assembling it As a compromise o
15. Effluent flowing through a screen at the outlet of the septic tank is at very low head and therefore particles cannot be forced through the openings In addition servicing the screen does not involve pump control floats wiring and discharge pipes Below are listed some specific criteria for baffle screens that meet the standards Maximum mesh opening of 1 8 inch protects discharge orifices of 3 16 inches or larger and pumps with the capacity to pass up to a 1 8 inch sphere For orifices smaller than 3 16 inches diameter the screen should have a mesh size of 1 16 inch smaller than the orifice it is designed to protect Non corrosive material durability leads to improved product life span and performance Provide an open area flow capacity at least equal to the flow capacity provided by a 4 inch diameter PVC pipe The minimum area will very likely require a high frequency of cleaning and therefore not meet the standard of performance between service intervals In standard practice a much larger flow area is used The larger flow areas will result in longer intervals between services for the same hydraulic and organic strength loadings The screen must be securely fastened to prevent dislodging or misalignment this relates to long term performance and servicing Be easily removable and or designed constructed and installed for easy and thorough cleaning this relates to long term performance and servicing Draw liquid from the clear
16. Feet Fig A 3a Minimum lateral diameter based on orifice spacing for 3 16 in diameter orifices Wisc Dept Of Commerce 1999 17 0 5 1 1 5 2 2 5 Orifice Spacing In Feet Fig A 3b Minimum lateral diameter based on orifice spacing for 3 16 in diameter orifices Wisc Dept Of Commerce 1999 140 120 0 5 1 1 5 2 2 5 Orifice Spacing Feet Fig A 4a Minimum lateral diameter based on orifice spacing for 1 4 in diameter orifices Wisc Dept Of Commerce 1999 Orifice Spacing in Feet Fig A 4b Minimum lateral diameter based on orifice spacing for 1 4 in diameter orifices Wisc Dept Of Commerce 1999 20 References Converse J C 1974 Distribution of domestic waste effluent in soil absorption beds Trans Of the ASAE 17 299 304 Converse J C 1999 Septic tanks and pump chambers with emphasis on filters risers pumps surge capacity and time dosing Small Scale Waste Management Project 345 King Hall University of Wisconsin Madison 1525 Linden Drive Madison WI 53706 Converse J C and E J Tyler 2000 Wisconsin Mound Soil Absorption Systems Siting Design and Construction Small Scale Waste Management Project 345 King Hall University of Wisconsin Madison 1525 Linden Drive Madison WI 53706 Publication No 15 22 Falkowski G M and J C Converse 1998 Siphon performance and pressure distribution for on site systems In On site Wastewater Treatment Proceedings of the Fifth National S
17. Page 49 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 2 Orifice Discharge Rates gpm Orifice Diameter in 0 09 098 08 LI 1 26 L 8 1 49 i 081 200 9 05 086 14 169 1 78 1 4 1 04 1 28 1 47 1 65 1 80 1 95 2 08 2 21 2 33 For residuals greater than 10 feet or for orifice diameters greater 1 4 inch the equation must be used This is also true if the residual pressure is not a whole number For large systems use the equation and verify with Table A 2 Note Table A 2 was generated assuming that the minimum residual head at the distal orifice is 5 feet when orifices are 1 8 and 5 32 inch in diameter and 2 feet for larger orifice diameters WA DOH Publication 337 009 Page 50 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 A 3 FRICTION LOSS DESIGN AID Friction losses in pipes can be calculated using the Hazen Williams formula Original form V 1 318 C 954 Where V velocity ft sec C Hazen Williams flow coefficient unitless hydraulic radius ft ft S slope of energy grade line ft 1000 ft This equation can be modified through algebraic substitutions and using unit conversions to yield a formula that directly calculates friction
18. UP TO SOIL dpi ae TREATMENT AREA FOR PLASTIC PIPE gt PROPER DRAINBACK IF PIPE AT TANK MUST BE Lower THAN UNION TO GET ELEVATION FOR DRAINBAEK Va INCH WEEP HOLE MUST ALARM FLOAT ON SEPARATE BE USED ELECTRICALCIRGUIT WEEBAMOLE START LEVEL a NOTES ELECTRICAL WIRE FROM POWER SUPPLY MUST NOT RUN OVER ANY TANKS 3 SHUT OFF LEVEL BUT MUST BE LAID BESIDE OTHER TANKS AND MUST BE PLACED IN CONDUIT ALONG POST PUMP CONTROL FLOAT ELECTRICAL CORDS FROM PUMP AND FLOATS MUST BE RUN THROUGH CONDUIT WIRES CANNOT HAVE GROUND CONTACT Figure X 8 Section of Pump Tank Showing Wiring and Electricity Away from House 12 02 PUMPS AND HYDRAULICS X 11 configuration is called the lead pump and the lag pump duplex control panels should be wired to operate in this way PUMP PRESSURE AND FLOW For dosing the absorption field the pump station should be designed to provide a pump out volume of 25 of the daily design flow The daily sewage flow from a four bedroom home is 600 gpd Thus the start and stop levels should be set to pump 0 25 x 600 gpd 150 gallons The setting of the pump control depends on the surface area of the tank For example if a pumping tank is rectangular with inside dimensions of 4 by 5 feet the surface area is 20 square feet Since each cubic foot of water contains 7 5 gallons 1 foot depth of liquid in this tank would contain 7 5
19. a 2 by 3 rectangular area With an absorption area of 6 ft wide with one lateral down the center perforation spacing would be 1 ft apart and the perforation would serve an area of 6 by 1 ft which would be undesirable Perforation size Smaller diameter perforations may reduce system discharge flow rate reduced pump requirements at the same time increasing the number of orifices benefitting equal distribution through out the system This example uses 3 16 perforations 4 Determine the lateral diameter Using Fig A 2a 3 16 to determine the minimum lateral diameter The laterals on each side of the center manifold each has the length of 56 ft with 3 ft spacing between orifices these point to a lateral diameter of 1 5 5 Determine number of perforations per lateral and number of perforations Using 3 0 ft spacing in 56 ft a lateral yields 19 perforations each p x 0 5 56 3 0 0 5 19 perforations lateral Number of perforations 4 lateral x 19 perforations lateral 76 Check Maximum of 6 perforation Number of perforations 412 sqft 6 f 75 76 gt 75 is okay 6 Determine lateral discharge rate LDR Using network pressure distal pressure of 3 5 ft and 3 16 diameter perforations Table A 1 gives a discharge rate of 0 78 gpm regardless of the number of laterals LDR 0 78 gpm perforation x 19 perforations 14 8 gpm lateral 7 Determine the number of laterals This was determined in Step 3 and 4
20. are slower to enter the fully pressurized phase which can result in somewhat unequal distribution on a sloped site and d the available head to pressurize the system is fixed and therefore design and installation errors cannot be overcome by increasing the pressure head WA DOH Publication 337 009 Page 60 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Appendix E References Converse J C 1974 Distribution of Domestic Waste Effluent in Soil Absorption Beds Transactions of the America Society of Agricultural Engineers Vol 17 No2 pp 299 309 Converse J C J L Anderson W A Ziebell and ZJ Bouma 1975 Pressure Distribution to Improve Soil Absorption systems Home Sewage Disposal Proceedings National Home Sewage Disposal Symposium American Society of Agricultural Engineers St Joseph MI pp 104 115 Otis R J J C Converse B L Carlisle and J E Witty 1978 Effluent Distribution Home Sewage Treatment Proceedings of the 2 National Home Sewage Treatment Symposium American Society of Agricultural Engineers St Joseph MI pp 61 85 WA DOH Publication 337 009 Page 61 of 61 APPENDIX O VII PRESSURE DISTRIBUTION NETWORK DESIGN Septic tank effluent or other pretreated effluent can be distributed in a soil treatment dispersal unit either by trickle dosing or uniform distribution Trickle flow known as gravity flow occurs each time was
21. become more common for use in individual homes The grinder pump is equipped with blades mounted on the impeller which literally grind up and shred solids before they enter the impeller The grinder pump must grind up the solids to a size that will not clog the impeller Two types of grinder pumps are currently available a centrifugal grinder pump and a positive displacement grinder pump The centrifugal grinder pump is more common but this pump usually is not capable of pumping against a high head However the positive displacement grinder pump can handle a high head application Regardless of the type of grinder pump used the blades will need to be replaced and the pump will require maintenance Some grinder pumps require a great deal of maintenance and repairs can be very expensive The grinder pump is most commonly used to convey wastewater into a small diameter sewer which serves some type of central wastewater treatment facility A pump handling solids or ejector pump is commonly used to deliver wastewater from a basement into a septic tank This type of pump system must be designed to deliver the required volume during each pump cycle without any drain back from the line into the septic tank Ejector pumps are usually equipped with a check valve to prevent this from happening When sewage is pumped into a septic tank turbulence is created in the septic tank For this reason the septic tank should have at least two compartments or have two ta
22. but will not allow water from the rest of the absorption field to drain back into the pump The distribution box should be arranged so that effluent from the discharge pipe from the pump is directed to the wall of the drop box opposite from the inlet pipe The outlet lines to the absorption field are then located on the sides of the box at a 90 degree angle from the inlet pipe If this arrangement is not carefully designed flow from the distribution box will not be evenly distributed If additional trenches need to be supplied in a pumped system then a series of drop boxes see Figure X 3 as shown in Figure X 1 may be used to direct the flow through the absorption field 12 02 Pumps AND HYDRAULICS X 3 OUTLET TO TRENCH SUPPLY LINE TO NEXT DROP Box yy OUTLET TO TRENCH SUPPLY LINE PIPE FROM PUMP SUPPLY LINE OUTLETS TO TRENCH 1 1 2 DR 2 PLASTIC 1 ALL PIPES OTHER THAN PRESSURE PIPE SHOULD BE AT LEAST 4 INGH DIAMETER 2 ELEVATION OF INLET AND SUPPLY LINE TO NEXT DROP BOX MAY BE ADJUSTED UP OR DOWN FOR DESIRED EFFLUENT LEVEL IN TRENCH 3 SUGGESTED TRENGH LIQUID LEVEL IS AT TOP OF TRENGH ROCK IF PERMEABLE SYNTHETIC FABRIC COVERS ROCK AT TOP OF OUTLET PIPE IF HAY OR STRAW COVERS ROCK 4 INVERT OF PIPE FROM PUMP MUST BE AT LEAST TWO INCHES HIGHER THAN INVERT OF SUPPLY PIPE TO NEXT DROP BOX 5 TRENGHES MAY OUTLET ONE SIDE OR BOTH SIDES OF DROP BOX OUTLET TO
23. called the squirt test The difference in orifice discharge rate must not exceed 1096 within in one lateral and may not exceed 1596 over the whole system Once the pressure is adjusted so that the minimum residual pressure is equal in all the lines then the system should be tested to see that the actual volume of discharge does not vary over 15 This is especially important in systems on a steep slope where the system is designed to drain back between dosing cycles In this type of system the lower elevation lateral Pumps HYDRAULICS X 30 12 02 ONINNIDSS 38 LESNA dale TWVH3AIVv1 Nl 31DH LSVv1 ANY LS5JU 310N OL va H LHY galos sagNnlgna ddang NEN NEN 481 Tvhi341vi4 alyva siyeavs 11W NIW 21 39V WbhsoVvYg QqQNfI1OdHEg HS aask BH AO a Manifold and Connection to Low Pressure Lateral Supply 16 Figure X 12 02 Pumps AnD HYDRAULICS X 31 6 W CAP FLUSH W GROUND SURFACE SCREW CAP ADAPTER LATERAL 1 Pvc ELBOW will pressurize first and receive effluent for a longer period of time In addition the lower lateral E dditional flow from the manifold or from the upper laterals cycle can be
24. design elements cause the siphon to produce the performance of 2 5 2 1 Where siphons are used the following requirements apply 2 5 3 1 The area to be dosed must be downhill from the siphon chamber and according to manufacturer s instructions for minimum elevation differential 2 5 3 2 effluent must be screened before entering the siphon chamber 2 5 3 3 The siphon must be installed to allow access for maintenance and cleaning WA DOH Publication 337 009 Page 22 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 5 3 4 dose counter s must be incorporated into the design and installation 2 5 3 5 Siphons can only be used where timed dosing is not required or where some system or arrangement delivers effluent to the siphon chamber evenly over a 24 hour period and no more than the maximum design flow for the system These criteria can be met by the use of a small electric pump which delivers effluent to the siphon chamber evenly over a 24 hour period This pump is sized to deliver no more than the daily design flow to the siphon chamber in a 24 hour period The siphon then doses a sand filter mound or sand lined drainfield 2 5 3 6 Siphons may only be used where they will be monitored and managed to the satisfaction of the local health officer Other important considerations e Proper siphon size must be select
25. difference must not exceed 21 10 flow difference between orifices on any one lateral The squirt height difference over the entire system must not exceed 32 15 flow difference Remember to use a new drill bit during construction The following table gives the actual distances Maximum Flow Difference Allowed Inches Nominal Residual Squirt Height 10 Flow Difference 15 Flow Difference 2 Feet 5 Inches 7 5 Inches 5 Feet 12 5 Inches 19 Inches 1 2 1 A minimum residual pressure of 0 87 psi 2 feet of head is required for systems with 3 16 inch diameter orifices and larger and 2 18 psi 5 feet of head is required for systems with orifices smaller than 3 16 inch Generally the testing should verify that distribution is uniform with the required minimum residual pressure that the system is dosed at the proper volume and frequency and that the alarms are functioning properly Suggested methods are provided below If problems are encountered during testing the installer should notify the designer or engineer Wiring problems should be referred to the electrician Described below are the steps for conducting a pressure test Q Measure squirt height Minimum squirt height for orifice size 3 16 orifice size 2 or 24 squirt height 1 8 orifice size 5 or 60 squirt height 5 32 orifice size 5 or 60 squirt height a Check uniformity of squirt height WA DOH Publication 337 009 Page 11 of 61
26. filter from hydraulic surges and overload Does not meter the effluent to the receiving component throughout a 24 hour period instead delivers the dose whenever a dose volume accumulates in the pump chamber Household water use patterns are usually in morning evening and weekend surges 2 Timed Dosing Meters the effluent to the receiving component in discrete evenly spaced doses Allows more frequent smaller doses to be pumped to the receiving component thereby promoting unsaturated flow through the soil or filter media Protects the receiving component from hydraulic overload Sensitive to heavy use days and therefore may often activate the alarm circuit when the volume of wastewater exceeds the design flow Some causes are weekend guests large laundry days parties and leaking fixtures More costly and complicated installation and maintenance Can be used to help detect groundwater leaking into the septic tank or pump chamber 3 Reduced Dose Volumes a More frequent smaller doses with intervening resting and aeration periods are pumped to the receiving component thereby assuring unsaturated flow through the soil or filter media May require smaller orifices smaller transport and lateral pipes check valves and orifices in the 12 o clock position in order to reduce the flow rate and to maintain the system full of effluent between doses The smaller orifices will increase the frequency of maintenance due to clogging Li
27. gal x 20 sq ft 150 gallons Thus to pump 150 gallons would require that the pump start level be 1 foot above the pump stop level In most domestic applications the pipe from the pumping station is buried only deep enough to prevent physical damage and on enough of a slope to drain back to the tank after each pump operation If exactly 150 gallons is pumped then with the drain back less than 150 PUMPING STATION ALTERNATING DUAL PUMPS SWITGHES AND OTHER CONTROLS IN WEATHER PROOF ENCLOSURE OR IN NEARBY BUILDING MANHOLE COVER SECURED TO PREVENT UNAUTHORIZED ENTRY JUNCTION SOLDER ALL WIRE GONNECTIONS UNIONS OR OTHER Quick DISCONNECT COUPLERS CHECK VALVES RESERVE CAPACITY AFTER ALARM SOUNDS WARNING CONTROL ON SEPARATE CIRCUIT Son k TREATMENT AREA M M 1 4 WEEPHOLE IF PIPE TO SOIL TREATMENT AREA Is NOT FROST PROOFED Pumps amp OPERATE ON ALTERNATE CYCLES IF EITHER PUMP FAILS TO OPERATE THE OTHER WILL OPERATE AND AN ALARM IS ACTUATED TO WARN OF FAILURE Figure X 9 Duplex Pump Station has Two Alternating Pumps 12 02 Pumps HYDRAULICS X 12 gallons will be pumped to the absorption field The volume of drain back must be calculated based on the capacity and length of the pipe to the distribution box This volume must be added to the volume to be pumped to provide a total pum
28. head of 26 6 feet This point located on the curves in Figure X 10 falls above the characteristic curves of the 1 3 horsepower and the 1 2 horsepower low head pumps Thus these pumps are not suitable for these pumping requirements If these pumps were the only ones available the flow would need to be reduced by using fewer or smaller perforations or in some cases the friction loss could be reduced by using a larger diameter pipe Since a requirement is to have slightly excess capacity to deliver flow at the Specified head select the pump curve just above the plotted head flow point 26 6 40 on Figure X 10 This point is above the low head curves but below the 1 2 horsepower medium head B Because discharge into a pressure distribution system is self balancing no valve is needed to reduce pressure While it can be exactly calculated by a trial and error solution the pump will likely deliver somewhat in excess of 45 gallons per minute at a total dynamic head of slightly more than 30 feet Again it is necessary to point out that the B 1 2 horsepower pump operates exactly on its own characteristic curve ENERGY REQUIREMENTS The amo nt of energy required for pumping sewage is relatively small If the pump delivers 40 gallons per minute and 174 gallons are to be pumped per dose then pump operating time is 4 35 minutes per cycle with 4 cycles per day for a total time of 17 4 minutes day The 7 horsepower pump will likely be equ
29. in the 6 o clock Position a When some or all of the orifices are in the down position the laterals will drain between dose cycles retarding the biological growth in them and reducing freeze up potential When the system drains a good rule of thumb for equal distribution is to design the dose volume to be at least 7 times the volume of the liquid that drains after a dose b When the orifice at the distal end farthest from the manifold is in the down position sludge in the lines tends to be driven to the distal end of the lateral and out the last orifice As that orifice clogs the next in line will clog and so on c Although systems with some or all of the orifices in the down position may be less prone to clogging they also will require a larger dose volume to pressurize the system due to laterals draining between pump cycles d Orifices in the down position cannot be directed to gravelless chambers and therefore will not have as wide a distribution pattern However there are special orifice shields available for orifices oriented in this position 6 Network Remaining Full or Partially Full Between Doses laterals can rarely be maintained at a level grade therefore some orifices will be lower than others so some of the effluent will drain out the lowest 12 00 o clock orifice a Allows smaller more frequent doses with intervening resting and aeration periods to be pumped to the receiving component thereby promoting unsaturat
30. is used the orifice spacing and lateral spacing are interrelated For absorption area widths of 3 feet one distribution pipe along the length requires an orifice spacing of 2 feet For a 6 ft wide absorption area with the same configuration it would require orifice spacing of 1 foot along the pipe 8 Calculate the manifold size and length Determine the main connection to the manifold center or end The point of the main manifold connection determines the length of the manifold The manifold length is measured from the main manifold connection to the end of the manifold The minimum manifold diameter can be determined from a chart and is based on the lateral flow rate lateral spacing and manifold length Table X 2 Orifice Discharge Rates in Gallons per Minute gpm Le ge m oss Ls ww o oae os os e pw se pos 12 02 Pumps HYDRAULICS X 20 Table X 3 Friction Loss in PVC Plastic Pipe feet 100 ft of pipe ____ Nominal Pipe Size inch pum pop 130051 74 250 C 3584 884 299 12 4210 1039 3531 L8 as 12 01 407 dil 14 5600 1381 46607 192 15 6363 1569 5 N 16 17169 1768 kasip 2617 17 8020 1978 BP eos 315 248 19 55955 998 0 gt 52 19 30487
31. loss _ 10 46LQ Where f friction loss ft D actual inside pipe diameter in L length of pipe ft Q flow gpm C Hazen Williams flow coefficient unitless The Hazen Williams flow coefficient C depends on the roughness of the piping material Flow coefficients for PVC pipe have been established by various researchers in a range of values from 155 to 165 for both new and used PVC pipe A coefficient of C 150 generally is considered to yield conservative results the design of PVC piping systems The equation shown above can be further simplified by assuming that only PVC pipe conforming to ASTM standard D 2241 or D 1785 for Schedule 40 and Schedule 80 pipe is used With this assumption the inside diameters D for the various nominal pipe sizes can be determined and combined with all other constants to yield the following equation hydraulic radius cross sectional area of the conduit divided by the inner perimeter of the conduit Analysis of Pipe Flow Networks Jeppson Ann Arbor Science Publications 1983 p 41 Handbook of PVC Pipe Design and Construction 2nd Edition Uni Bell Plastic Pipe Association 1982 WA DOH Publication 337 009 Page 51 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 f L Q K Where f friction loss through pipe ft L length of pipe ft Q flow gpm K Constant from Tabl
32. provide even effluent distribution Schedule 40 PVC pipe and fittings are typically used in low pressure onsite distribution systems Orifices holes are drilled perpendicular to the pipe and are placed on the pipe invert underside or top Any burrs or rough edges must be removed from the holes so they do not collect debris and clog Holes should be drilled carefully If the holes are not very close to the size specified in the design the discharge will be different and will alter the performance of the system PRESSURE DISTRIBUTION NETWORK DESIGN The following design is for the mound system describedin Chapter VI pages 8 to VI 26 However a very similar design procedure is used for any pressure distribution network including sand filter media filter low pressure laterals or drip dispersal Pipe Network Design Steps 1 Refer to the mound design to determine the absorption bed area A x B The network configuration and length of the laterals will be based on the absorption bed area The absorption area width will determine how many parallel lines will be used for the distribution network The lateral length is measured from the distribution manifold to the end of the lateral A center manifold is preferred because it minimizes pipe sizes Remember all lateral lines are to be on the same elevation or the operating head must be adjusted so they are equal 2 The spacing between lateral lines should always be less than 5 feet Spaci
33. sesal 19 0 787 194 MEA 06 25 4 3235 1340 330 45 4045 1666 411 4915 9 60 W 528936 700 097 3 T dq 931 429 as Ue ee ee ee _ 7 90 M8 20 O 10 180 250 062 D5 272 378 093 Laud es ocn Note This is confusing these values do not agree with those in Table X 1 Which is correct 12 02 Pumps HYDRAULICS X 21 Determine the network discharge rate This value is used to size the pump or siphon Take the lateral discharge rate and multiply it by the number of laterals or take the perforation discharge rate and multiply it by the number of perforations 9 Develop a system performance curve This performance curve is a way to predict how the distribution system performs under various flow rates and heads The flow rate is a function of the total head that the pump works against As the head becomes larger the flow rate decreases but the flow rate determines the network pressure and thus the relative uniformity of discharge throughout the distribution network The easiest way to select the correctly sized pump is to evaluate the system performance curve and the pump performance curve Where the two curves cross is where the system operates relative to flow rate and head The total dynamic head that the pu
34. sufficient number to meet the design needs of the system As the number of dose cycles increases the amount of effluent delivered per dose must decrease in order to prevent more than daily design dose from being delivered to the drainfield Delivering more than 6 or 8 doses per 24 hours will require one or more of the following features to be designed into the system e orifices at 12 00 o clock to keep the piping network full or mostly full of effluent between doses to reduce the volume per dose e transport manifold and lateral pipe diameters are reduced to reduce the volume per dose e orifice size is reduced to help reduce the volume per dose e fluid velocity in pipes is increased to help scour the pipe and as a consequence of the reduced pipe size e residual hydraulic head at the orifices is increased to help clear the smaller orifices e check valves are placed into the system to prevent flowback to reduce the volume per dose e aperformance test of the check valves as many do not perform as intended 2 5 1 2 2 When the treatment component is timed dosed prior to a soil dispersal component the soil dispersal component does not need separate timed dosing In this case only a demand dosing system with a dose cycle counter and hour meter or a water meter on the water supply or sewage stream is required for the soil dispersal component 2 5 1 2 3 Demand controlled pressure distribution systems must include ele
35. suitable unsaturated soil provides adequate treatment of wastewater Research also indicates that the method of distribution of septic tank effluent within the soil absorption field can affect the system s treatment performance A frequently used and the simplest method for distributing effluent is gravity flow Gravity flow allows wastewater to flow by gravity through large diameter pipes into the subsurface soil absorption system Distribution is usually localized in a few areas within the field which results in overloading of the infiltrative surface in those areas until a mature biomat develops This overloading can lead to groundwater contamination in coarse granular soils due to insufficient treatment or more rapid clogging in finer textured soils A second method of distribution dosing can overcome some of these problems It is dealt with in a separate publication entitled Dosing Gravity Drainfield Systems revised July 2007 Because effluent is distributed over a larger portion of the absorption area and the period between doses is maximized the degree of soil clogging is reduced However localized overloading may still occur A third method is pressure distribution which comes closest in achieving uniform distribution WA DOH Publication 337 009 Page 8 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Pressure distribution is usually used in locations where
36. the pressure at the perforations also increases and the pump simply operates at a particular point on its own particular characteristic curve A gate valve is not needed with a pressure distribution system 12 02 Pumps AnD HYDRAULICS X 13 HEAD PUMPS FEET v Ve Ve va HP A HP B HP G FLOW IN GPM gt lt 10 69 77 63 70 15 72 54 A 20 61 65 2s 25 ed NC 52 50 ee 43 26 sn 35 TOTAL DYNAMIC HEAD IN FEET 10 H Du 2 n 20 5n 4 70 90 100 Dis ALLO ER MINUTE GPM Figure X 10 mple Pump Pumps Two Low Head with Different Size Motors a M Head and a Higher Head Pump 12 02 Pumps AnD HYDRAULICS X 14 Table X 1 Schedule 40 Plastic Pipe Friction Loss Diameter and Volume Pipe Diameter 1 1 25 1 5 27 2 5 3 Inside dia 1 05 1 38 1 61 2 067 2 47 3 07 4 03 Gals 100ft 4 4 7 8 10 6 17 4 24 9 38 4 66 1 Friction Loss in ft 100ft 1042 x Q 4 where Q Flow gpm Internal Pipe Diameter inches c Pipe Constant 150
37. 2 Orifice Discharge Rates gpm Head ft Orifice Diameter in 8 1 4 0359 00 104 o 08 128 03 13 14 064 095 16 1465 po p 041 064 045 7 049 06 110 19 195 2052 osn 117 10 2 08 oss 06 14 1609 221 058 04 11 178 255 For residuals greater than 10 feet or for orifice diameters greater than 1 4 inch the equation must be used This is also true if the residual pressure is not a whole number For large systems use the equation and verify with Table A 2 0 45 Note Table A 2 was generated assuming that the minimum residual head at the distal orifice is 5 feet when orifices are 1 8 and 5 32 inch in diameter and 2 feet for larger orifice diameters WA DOH Publication 4337 009 Page 50 of 61 Chapter Pumps and Hydraulics INTRODUCTION X 1 PUMP APPLICATIONS X 1 PUMP TANKS X 4 PUMP TYPES X 8 PUMP CONTROLS X 8 PUMP PRESSURE AND FLOW X 11 PUMP DISCHARGE CURVE X 12 SELECT THE PUMP FOR THE APPLICATION X 15 ENERGY REQUIREMENTS X 16 PRESSURE DISTRIBUTION NETWORK X 17 PRESSURE DISTRIBUTION NETWORK DESIGN X 18 Pipe Network Design Steps X 18 Sizing the Pump or Siphon 21 DESIGN EXAMPLE X 22 Distribution Network Design Steps X 22 Force Main Pressurization Unit Dose Tank and Controls Design Steps X 24 LOW PRESSURE PIPE SYSTEM X 27 Components X 27 Performance Testing X 29 Maintenance X 32 Low Pressure Pipe Design Example X
38. 5 Size the dose tank The pump tank size should be based on the dose volume 24 hour storage volume and room for a block beneath the pump and control space This example is for a residential application additional information on dosing requirements can be found in Section E of the manual 6 Select controls and alarm Time Dosing The advantage of time dosing provides more frequent doses and levels out peak flows to the bed CONSTRUCTION AND MAINTENANCE Good common sense should prevail when constructing and maintaining these systems Water tight construction practices must be employed for all tanks Surface runoff must be diverted away from the system Any settling around the tanks must be filled with the soil brought to grade or slightly above to divert surface waters Table A 1 Perforation Discharge Rates GPM Distal Perforation Diameter in Pressure ft 1 8 5 32 3 16 1 4 5 16 3 8 o 1 0 0 18 0 29 0 41 0 74 1 15 1 66 1 3 0 23 0 35 0 50 0 90 1 41 2 03 2 0 0 26 0 41 0 58 1 04 1 63 2 34 2 5 0 29 0 45 0 66 1 17 1 82 2 62 3 0 0 32 0 50 0 72 1 28 1 99 2 87 25 0 34 0 54 0 78 1 38 2 15 3 10 4 0 0 37 0 57 0 83 1 47 2 30 3 32 4 5 0 39 0 61 0 88 1 56 2 44 252 5 0 0 41 0 64 0 93 1 65 2 57 3 71 Values were calculated as 11 79 x d x Nh Where d orifice dia in inches and h head feet Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A
39. 5 85 85 6 84 96 96 1 4 15 52 5 55 5 58 5 2 64 68 70 2 5 72 5 775 80 3 J 87 90 4 100 104 108 5 115 120 125 6 126 138 m WA DOH Publication 337 009 Page 48 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 A 2 ORIFICE DISCHARGE RATE DESIGN AID Orifice discharge rates can be calculated using Toricelli s equation Q Ca Ao 2g h Where the discharge rate in ft sec the discharge coefficient unitless A the cross sectional area of the orifice in fe g the acceleration due to gravity 32 2 ft sec h the residual pressure head at the orifice in ft The formula shown above can be simplified for design purposes by incorporating the discharge coefficient and using conversion factors so that the discharge is given in gallons per minute and the orifice diameter is given in inches The discharge coefficient depends on the characteristics of the orifice and is usually determined empirically This value can range from 0 6 to 0 8 but a value of 0 6 was assumed for the purpose of this design aid The formula therefore simplifies to 0 1 7947 Where the orifice discharge rate in gpm d the orifice diameter in inches h the residual pressure head at the orifice in feet On the next page Table A 2 gives orifice discharge rates in gpm generated using the above formula for various residual pressures head and orifice diameters WA DOH Publication 337 009
40. 5 ft length for a 2 inch diameter manifold at 50 gpm See Table X 2 to find the friction loss per 100 ft of the supply line b Friction head 35 ft supply line length x 3 98 ft head x 1 25 fitting adj 100 ft 12 02 Pumps AnD HYDRAULICS X 33 1 68 ft head c Total head 20 ft elevation head 1 68 ft friction head 4 ft pressure 25 68 ft Dosing Volume a 2 4 doses per day based upon use b Volume in lateral lines 4 1 gal 100 ft of 1 inch pipe Table VII 7 x 360 ft of lateral pipe 100 ft of pipe 14 76 gallons c Volume in supply line 16 2 gal 100 ft of 2 inch pipe x 35 ft supply line 100 ft of pipe 5 67 gallons d Total volume in system volume of laterals 14 67 gal volume of supply line 5 67 gal 20 43 gallons e Volume of void space in trench cross sectional area 0 5 ft x 0 5 ft x 360 ft length x 7 48 gal ft 90 ft x 7 48 gal ft 673 2 gal Trench should have approximately 30 void space 673 2 gal x 30 201 gal As long as the void space in trench is smaller than the gallons per dose the system will function Based upon these calculations the pump must be sized to supply 50 6 gpm at 26 ft TDH Total Dynamic Head Table X 6 Orifice Flow Rate in gallons per minute gpm for Different Sizes and Pressure Head BOE c Xo ow w a 1l Ll o8 20 10 hd5P 05 e 130 1 AEN NES
41. 724 requires timed dosing in the soil dispersal component for all sites where technologies meeting Treatment Levels A or B are mandated soil dispersal components having daily design flows between 1000 and 3500 gallons of sewage per day and in the soil dispersal component following all repairs using the allowances of Table IX in WAC 246 272A 0280 Technologies such as sand filters recirculating gravel filters sand lined trenches mounds and other treatment components also require timed dosing in order to assure those technologies meet treatment requirements or expectations For systems requiring time dosed pressure distribution accessible controls and warning devices are required and must 2 5 2 1 1 meet the functional requirements for pressure distribution 2 5 2 1 2 deliver prescribed dose sizes uniformly to the orifices in the distribution network 2 5 1 2 1 3 deliver the effluent to the distribution network in evenly spaced doses over a 24 hour period 2 5 1 2 1 4 provide prescribed resting periods between doses 2 5 1 2 1 5 assures no more than the design volume for each 24 hour period is delivered to the receiving component 2 5 1 2 1 6 record and store the pump run time and number of dose cycles 2 5 1 2 1 7 have controls and components listed by Underwriter s Laboratory or equivalent and 2 5 1 2 1 8 alarm circuit independent of the pump circuit WA DOH Publication 337 009 Page 19 of 61 Pr
42. 9 Un 555 58 5 552 14 2 58 6 70 5502 25 675 775 80 sm 3 75 9 90 114 4 92 108 sm ii 5 15 120 125 532 11 816 10 138 144 5522 172 15 705 73 5 502 112 1 2 76 8 88 5502 11 2 25 875 975 102 5 sm 1i 3 T 9 1i 114 rmi uox 136 a E Os 160 sm ii Be 4 180 5322 2 J 15 96 105 106 5 E 128 582 121251135 1425 147 5 552 2 3 50 16 168 5322 2 4 14 19 200 502 2 15 20 25 235 sm 2 s 2 264 316 1 15 24 30 316 1 2 28 36 316 1 25 35 425 36 1 3 T 39 T 4 316 1 124 44 56 52 x6 1 6 o 7 x6 i5 15 95 45 25 WA DOH Publication 337 009 Page 45 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 1 Lateral Design Table continued Maxim Lateral Length 00 Orifice Spacing Pipe Material Schedule 40 Class200 Class 160 54 56 62 5 62 5 316 15 3 o 6 72 84 88 95 100 316 125 6 96 108 114 55 5 57 316 15 2 60 6 70 71 5 80 87 90 104 108 120 125 316 15 6 10 15 144 81 84 98 102 112 5 117 5 129 132 152 160 180 185 316 2 6 18 19 210 ma 1 s Bs oa 3 x
43. BOX SLOPING GROUND MANIFOLD BELOW LATERALS FIGURE 6A WA DOH Publication 337 009 Page 37 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 TO DRAINFIELD RISER WITH LOCKING LID PRESSURE LATERALS A A i i l FLOW CONTROL VALVE SLOTS AS REQUIRED 2 ROX LONG SWEEP 90 5 SI DEGREE ELBOW 4 A HU SECTION A A WASHED ROCK DRAIN SUMP TRANSPORT PIPE FROM PUMP CHAMBER DRAINFIELD CONTROL BOX SLOPING GROUND MANIFOLD ABOVE LATERALS FIGURE 6B WA DOH Publication 337 009 Page 38 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Original Ground Surface Original Ground Surface Orifice shield Lateral Orifice with Cap Trench Detail Orifice covered by 2 6 PVC pipe cut in 1 2 N T S Orifice with Cap Trench Detail N T S Original Ground Surface 6 PVC cut in half Pressure line in 6 PVC 1 2 shell braced to prevent line shifting Orifice with Cap Trench Detail N T S Original Ground Surface Original Ground Surface Lateral le Pressure line suspended per manufacturer specifications Pressure line to be cross braced to prevent line shifting Orifices must be oriented in the 12 00 position Orifices must be oriented in the 12 00 position Gravelless Trench Detail
44. Gravelless Trench Detail N T S N T S Orifice Caps and Shields FIGURE 7 _ METER BOX OR ud OTHER ENCLOSURE Y THREADED CAP Ea ORIFICE SHIELD GRAVEL CLEANOUT AND MONITORING PORT FIGURE 8A WA DOH Publication 337 009 Page 39 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 THREADED CAP OR PLUG PLUG IN SLEEVE 6 PVC LAST ORIFICE WITH ORIFICE SHIELDS IF ORIFICE ORIENTATION IS BACKFILL MATERIAL 7 S E Q x N 6 zd N SU ISI S VINOS PSY 000 P PRESSURE LATERAL 5592000 AS SPECIFIED PVC HOSE OR BC LONG SWEEP aos ELBOW DRAIN ROCK 6 MIN BELOW PIPE UNDISTURBED SOIL 6 PVC WITH DRAIN HOLES EXTEND TO BOTTOM OF GRAVEL TO MONITOR PONDING INFILTRATIVE SURFACE MONITORING CLEANOUT PORT EXAMPLE FIGURE 8B WA DOH Publication 337 009 Page 40 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 BELL TRIGGER TRAP E Z lt VENT PIPE DRAWDOWN SNIFTER PIPE INTRUSION PIPE lt DISCHARGE OUTLET INLET PIPE a TRAP DEPTH LONG LEG SHORT LEG TRAP EXAMPLE OF SIPHON FIGURE 9 WA DOH Publication 337 009 Page 41 of 61 Pressure Distribution Systems
45. PIPE FROM PUMP CHAMBER DOWN SLOPE GRADIENT HEADER MANIFOLD PIPE FEATURES 1 FLOW IS CONTROLLED TO EACH LATERAL BY FLOW CONTROL LATERAL FEEDER PIPES VALVE 2 BACKFLOW IS PREVENTED BY MANIFOLD POSITION ABOVE LATERALS LEGEND 3 ACCEPTABLE VARIANCE OF DOSE TO EACH LATERAL MAY BE IMPOSSIBLE DUE TO CHECK VALVE v DIFFERING VOLUMES WITHIN EACH OF 2 LATERAL FEEDER PIPES ALL OF UE ANE WHICH DRAIN AFTER PUMP CYCLE PRESSURE DISTRIBUTION DRAINFIELD SLOPING GROUND FIGURE 3B WA DOH Publication 337 009 Page 35 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Manifold Below WA DOH Publication 337 009 e Check Valve inier d E EN Manifold installed below freezing depth Nx Flow Control Valve 2 Check Valve Pressure Drainfield vaio Tee To Tee Figure 4 NS Threaded Cap or amp Pressure Drainfield Cross Construction Figure5 Page 36 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 RISER WITH LOCKING LID TO DRAINFIELD PRESSURE LATERALS FLOW CONTROL VALVE SLOTS AS REQUIRED FLAPCHECK gt VALVE NN LONG SWEEP 90 N OY DEGREE ELBOW Gow SECTION A A WASHED ROCK DRAIN SUMP TRANSPORT PIPE FROM PUMP CHAMBER DRAINFIELD CONTROL
46. TRENCH DROP BOX FOR PUMP EFFLUENT Figure X 2 Pump Discharge Delivery to a Gravity Distribution Lateral Drop Box 12 02 Pumps AND HYDRAULICS X 4 1 ALL PIPES SHOULD BE AT LEAST 4 INEH DIAMETER c OUTLET TO TRENCH 2 ELEVATION OF INLET AND SUPPLY LINE TO NEXT DROP BOX MAY BE ADJUSTED UP OR DOWN FOR inter eee SUPPLY LINE DESIRED EFFLUENT LEVEL IN TRENGH TANK OR PREVIOUS aaa eae TO NEXT DROP DROP Box 3 SUGGESTED TRENCH LIQUID LEVEL IS AT OF TRENCH ROCK IF PERMEABLE SYNTHETIC FABRIC COVERS ROCK AT TOP OF OUTLET PIPE IF HAY OR STRAW COVERS ROCK 4 INVERT OF PIPE FROM PUMP MUST BE AT LEAST TWO INCHES HIGHER THAN INVERT OF SUPPLY PIPE Pree TO NEXT DROP T NS 5 TRENGHES MAY OUTLET ONE SIDE OR BOTH SIDES OUTLET TO TRENCH OF DROP BOX INLET SUPPLY LINE SUPPLY LINE DuTLETS TO TRENCH OUTLET TO TRENGH DROP Box Figure X 3 Gravity Distribution Lateral Drop Box PUMP TANKS The pump tank must be watertight and corrosion resistant Most pump tanks available today are concrete fiberglass or polyethylene All openings to the tank must be sealed and watertight to prevent the flow of groundwater or surface water into the tank and also to prevent the flow of wastewater out of the tank except through the pump discharge The pump tank must contain a minimum volume of water at all times in order to prevent the tank from fl
47. Use Table X 4 to develop a system performance curve Follow the procedures a Select 5 flow rates with 2 points above and below the network discharge rate of 60 gpm b Calculate the orifice perforation flow rate for each of the flows This is done by dividing the flow rate by the number of orifices in the network For the 30 gpm and 76 orifices the orifice flow rate is 0 395 gpm 12 02 Pumps HYDRAULICS X 25 c The elevation head is the height that the effluent is lifted The force main head is the head loss in the force main for the given flow rate Need to select a force main diameter For this example use 3 force main The first three flow rates are not on the chart and heads were calculated Normally the system is not operated in this range because velocities are less than 2 ft sec For the 60 gpm the friction loss is 0 97 ft x 1 25 for distance 1 21 ft Table X 4 Head and Calculations for Various Operating Flow and Pressure Flow EP M Flow gpm Head ft Difference ft Main Loss ft Head ft ox us us ae so e 3s GS om 59 oem se uus ome o wm s 3 5 e network head is calculated by 1 3 x Q 11 79x d is head in ft Q is orifice flow rate in gpm and D is orifice diameter in inches The 1 3 is an adjustment factor for friction loss in laterals For 3 16 diameter orifice the equation is
48. WAC and local jurisdictional rules If any provision of these recommended standards is inconsistent with local jurisdictional rules regulations ordinances policies procedures or practices the local standards take precedence Application of the recommended standards presented here is at the full discretion of the local health officer Local jurisdictional application of these recommended standards may be 1 Adopted as part of local rules regulations or ordinances When the recommended standards either as they are written or modified to more accurately reflect local conditions are adopted as part of the local rules their application is governed by local rule authority 2 Referred to as technical guidance in the application of the technology The recommended standards either as they are written or modified to more accurately reflect local conditions may be used locally as technical guidance Application of these recommended standards may occur in a manner that combines these two approaches How these recommended standards are applied at the local jurisdictional level remains at the discretion of the local health officer and the local board of health The recommended standards presented here are provided in typical rule language to assist those local jurisdictions where adoption in local rules is the preferred option Other information and guidance is presented in text boxes with a modified font style to easily distinguish it from the r
49. a tee to tee connection will trap the wastewater in the lateral lines which may create a problem during freezing conditions The ends of the laterals opposite from the supply end should be turned up and be equipped with a cleanout as shown in Figure X 17 The cleanouts should have a threaded or removable cap to allow for flushing the lateral lines and to monitor the head pressure in the laterals The yard box covering the cleanout should be at least 6 inches in diameter and must be readily accessible for maintenance If the orifices are placed in the 12 o clock position then orifice shields must be used to distribute the flow and keep small particles out of the orifice The design and construction of a low pressure pipe system includes determining the orifice size and spacing the dosing volume the lateral pipe size and sizing the pump of these factors must be incorporated into the design and included in the calculations of the friction loss in the pipe the drain back volume the dosing cycles and the operating pressure for the system A sample calculation fora low pressure pipe system is included to demonstrate how the tables shown are used to determine the various system components Performance Testing Since the low pressure pipe system is dependent upon equal flow distribution the system should be tested prior to covering the trenches to be sure that the system is properly functioning The most common way to test the system is commonly
50. adings and settings The owners of pressure distribution systems should be notified that their systems should be inspected and or serviced on a yearly basis 3 1 Evaluate Drainfield 3 1 1 for indications of surfacing effluent 3 1 2 for appropriate vegetation landscaping impacts ponds etc 3 1 3 for absence of heavy traffic 3 1 4 for inappropriate building 3 1 5 for impervious materials or surfaces 3 1 6 for abnormal settling or erosion 32 Evaluate Laterals 3 2 1 for residual pressure at the distal ends Confirm that it is the same as those recorded on the construction record If not the same laterals and orifices need to be cleaned 3 2 2 forequal flows in each lateral 3 2 3 for need for cleaning Clean laterals and orifices as necessary 3 3 Measure Pump Run Time per Cycle and Drawdown Compare these values with those recorded in the construction record If not the same evaluate the system for improperly set timer control float switches clogged laterals plugged orifices 3 4 Test Alarms Test alarms for proper functioning high and low liquid level WA DOH Publication 337 009 Page 30 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 3 5 Evaluate Septic Tank and Pump Chamber 3 5 1 for sludge and scum accumulations pump when the sludge and scum thickness total 1 3 of the depth of the tank 3 5 2 for clogging damage and proper placement of o
51. al discharge rate in gallons per minute 3 Lateral spacing in feet Example A Central manifold configuration lateral discharge Q 40 gpm lateral spacing 6 ft manifold diameter 4 inch Maximum length 18 ft Example B End manifold configuration lateral discharge Q 30 gpm lateral spacing 6 ft manifold length 24 ft Minimum diameter 3 inch WA DOH Publication 337 009 Page 56 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Appendix B Volume of Pipe gallons per foot pe Type of Pipe PR 160 PR 200 Schedule 40 in __ _ 0 008 6 1536 145 150 MEN pO 4018 BE 4 12 5 652 5432 po WA DOH Publication 337 009 Page 57 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Appendix C Advantages Disadvantages of Dosing Systems Demand Dosing Timed Dosing Reduced Dose Volumes Orifices in 12 00 o clock Position Orifices in 6 00 o clock Position Network Remaining Full or Partially Full between doses 1 Demand Dosing a b Least complex of control systems and therefore least costly to install and easiest to understand Not sensitive to heavy use days and therefore will not activate the alarm circuit with weekend guests large laundry days or parties Does not protect the drainfield mound or sand
52. alculate orifice discharge rates and includes a table of discharge rates for various residual heads and orifice diameters Appendix A 3 FRICTION LOSS DESIGN AID includes a derivation of an equation that can be used to calculate friction losses and a table of constants to simplify the calculation Also included is a table of friction loss for PVC pipe fittings Appendix A 4 MAXIMUM MANIFOLD LENGTHS lists the assumptions used to calculate the enclosed tables for maximum manifold length one for 1 8 inch and 5 32 inch orifices where the minimum residual head at the distal orifice must be 5 feet and one for orifices of 3 16 inch and up where the minimum residual head at the distal orifice must be 2 feet Throughout Appendix A it is assumed that laterals and manifolds will be constructed using only PVC pipe materials conforming to ASTM standards D 2241 or D 17635 A 1 LATERAL DESIGN TABLES The maximum allowable length for any lateral is determined by allowable differences in discharge rates between the proximal and distal orifices These tables assume that Q Qa lt 1 1 Where Q the proximal orifice discharge rate Qu the distal orifice discharge rate The maximum allowable difference in discharge rates is 1096 The maximum allowable lateral length is a function of lateral diameter and orifice diameter and is independent of the residual pressure Orifice discharge rates are a function of orifice diameter and residua
53. als were used on each side of center feed they would be spaced 1 5 ft apart 8 Calculate the manifold size Since there is only one lateral per each side of center feed there is no manifold Had two laterals been used the manifold could be the same size as the force main as it is an extension of the force main 9 Determine the network discharge rate NDR NDR Number of laterals X lateral discharge rate LDR 2 laterals x 29 6 gpm 59 2 or 60 gpm Pump has to discharge a minimum of 60 gpm against a total dynamic head yet to be determined 10 Total dynamic head is the sum of the following System head 1 3 x distal head ft 1 3 3 ft 4 5 ft Elevation head 9 0 ft Friction Loss Table 2 for 60 gallons and 125 ft 8 75 ft for 2 diameter Use 3 diameter unless pump can handle 1 21 ft for 3 diameter added friction loss of 2 in diameter pipe Total Dynamic Head 14 7 ft 3 force main or 22 3 ft 2 force main Pump must discharge 60 gpm against a head of 14 7 ft with 3 force main These are the calculated flow and head values The actual flow and head will be determined by the pump selected A system performance curve plotted against the pump performance curve will give a better estimate of the flow rate and total dynamic head the system will operate under The next section gives an example Force Main Pressurization Unit Dose Tank and Controls Design Steps 1 Calculate the system performance curve
54. ave to be made outside the dose tank There are excellent user friendly control panels for times dosed systems DESIGN EXAMPLE Design a pressure distribution network for mound whose absorption area is 113 ft long by 4 feet wide The force main is 125 feet long and the elevation difference is 9 ft from the lowest wastewater level in the dosing tank to the highest point in the main or manifold Distribution Network Design Steps l Configuration of the network This is a narrow absorption unit on a sloping site so use 1 or 2 lines with a center feed creating two laterals Determine the lateral length Using a center feed the lateral length is Lateral Length B 2 0 5 ft Where B absorption length 150 2 1 ft The 1 ft the distance from the end of the lateral pipe to the end of the gravel bed 74 ft Determine the perforation spacing and size Two examples A and B are included Perforation spacing Each Perforation covers a maximum area of 6 ft The absorption area is 3 ft wide a With one lateral down the center on each side of the center feed Spacing area per orifice width of absorption area 6 ft 3 ft 2 0 ft b With two laterals down the center on each side of the center feed Spacing area orifice x no of laterals absorption area width 6f X 2 3 ft 3 ft The designer may stagger orifice spacings with laterals 1 5 ft apart Perforation size Select from 1 8 3 16 or inch Us
55. ber of perforations B Design and Selection of the Force Main Pump Dose Chamber and Controls 1 Develop a system performance curve The system performance curve predicts how the distribution system performs under various flow rates and heads The flow rate is a function of the total head that the pump works against As the head becomes larger the flow rate decreases but the flow rate determines the network pressure and thus the relative uniformity of discharge throughout the distribution network The best way to select the pump is to evaluate the system performance curve and the pump performance curve Where the two curves cross is the point where the system operates relative to flow rate and head The total dynamic head that the pump must work against is the 1 System network head 1 3 x distal pressure 2 Elevation difference between the pump and the highest point in the system 3 Friction loss in the force main The system network head is the pressure maintained in the system during operation to assure relatively uniform flow through the orifices The 1 3 multiplier relates to the friction loss in the manifold and laterals which assumes that the laterals and manifold are sized correctly The elevation difference is between the pump and the highest point in the system in feet the pump industry uses the bottom of the pump tank The friction loss in the force main between the pump tank and the inlet to the network is determ
56. bution network i is a detailed procedure which involving flow rates pipe diameters number and size c orifices lateral pressure and pressure or head delivered by the pump Interrelationships are involved such as pipe size versus friction head loss The process may require t trying various com inations to come up with a design which produces an efficient system Howe e Ver tables ane charts have been developed to help determine appropriate combinations for common designs If the first design combination isn t satisfactory for some i reason such as requiring unusually expensive pump other combinations can be tried to see if improvements can be made pressure distribution network must be designed to ensure uniform distribution of the wastewater The pressure distribution system consists of 1 lateral pipes with equally spaced holes drilled into the invert of the pipe 2 manifold and main connected to the laterals 3 dosing or pump tank to collect septic tank effluent to be pumped to the mound 4 pump to pressurize the system and 5 controls alarm and power supply to operate the pump To avoid requiring a very large pump small diameter pipes usually 1 to 17 inch but 12 02 Pumps HYDRAULICS X 18 occasionally larger are used to distribute the wastewater The 4 inch lateral pipe used for gravity fed soil absorption systems is not suitable because it is too large and the holes are not appropriately sized or spaced to
57. c tank or other pre Solids separation and storage treatment device Screen Protect pump and distribution network orifices from solids Pump chamber surge tank Transport a specific volume of effluent from the Surge tank pump chamber to the distribution network Accumulate effluent between pump cycles and during malfunction Transport line Pipeline that connects the pump to the Manifold Manifold Piping network connecting the transport line to the various laterals Control Panel NEMA rated box containing all the controls for the pumping system dose cycle counter pump run time meter and alarm controls Laterals Small diameter pipes with orifices which distribute effluent within a trench or bed Drainfield Allows the septic tank effluent to pass into the native soil or other receiving media where various biological and physical processes provide additional treatment WA DOH Publication 337 009 Page 10 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 1 Performance Standards 1 1 Intent The intent of pressure distribution is uniform distribution of effluent throughout the receiving component 1 2 Measure of Performance The variation in orifice discharge rates within any one lateral must not be more than 10 The variation in orifice discharge rates over the entire distribution system must not be more than 15 The squirt height
58. ctrical control system that WA DOH Publication 337 009 Page 20 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 5 1 2 3 1 has the alarm circuit independent of the pump circuit 2 5 1 2 3 2 will meet the functional and reliability requirements for pressure distribution 2 5 1 2 3 3 has controls and components that are listed by UL or equivalent 2 5 1 2 3 4 is secure from tampering and resistant to weather minimum of NEMA 4 2 5 1 2 3 5 located outside within line of sight of the pump chamber 2 5 1 2 4 All control panels must have cycle counters and elapsed time meters for all pumps Alternatively a water meter on either the water supply or sewage streams will satisfy this requirement 2 5 1 2 5 All control panels must be equipped with both audible and visual high liquid level alarms and the alarms must be placed in a conspicuous location 2 5 1 2 6 Float switches must be mounted independent of the pump and transport line so that they can be easily replaced and or adjusted without removing the pump The minimum requirements for timed pump cycle controls are a timer actuator float for the pump and a high liquid level alarm In addition a low liquid level off float is highly recommended See next section Floats for a discussion 2 5 1 2 7 Electrical control and other electrical components must be approved by Underwriters Labo
59. d the tanks must be filled with the soil brought to grade or slightly above to divert surface waters Table A 1 Perforation Discharge Rates GPM Distal Perforation Diameter in Pressure ft 1 8 5 32 3 16 1 4 5 16 3 8 m CN TP Cente sepu ipe Er i 1 0 0 18 0 29 0 41 0 74 1 15 1 66 1 5 0 23 0 35 0 50 0 90 1 41 2 03 2 0 0 26 0 41 0 58 1 04 1 63 2 34 2 9 0 29 0 45 0 66 1 17 1 82 2 62 3 0 0 32 0 50 0 72 1 28 1 99 2 87 3 5 0 34 0 54 0 78 1 38 2 15 3 10 4 0 0 37 0 57 0 83 1 47 2 30 3 32 4 5 0 39 0 61 0 88 1 56 2 44 3 52 5 0 0 41 0 64 0 93 1 65 2 57 3 71 Values were calculated as gpm 11 79 d x Vh Where orifice dia in inches and head feet Table A 2 Maximum Manifold Length ft For Various Manifold Diameters Given the Lateral Discharge Rate and Lateral Spacing from Otis 1981 e Manifold Manifold Manifold Manifold Manifold Manifold Rate 8 Diameter 114 Diameter 12 Diameter 2 Diameter 3 Diameter 4 Diameter 5 Lateral Spacing Lateral Spacing Lateral Spacing Lateral Spacing Lateral Spacing Lateral Spacing Center ft ft ft A 24 6 8 10 24 6 8 10 24 6 8 10 24 6 8 10 24 6 8 10 24 6 8 10 Manifold 8 40 20 10 5 5 60 30 1 70 735 80 40 90 45 444242422 6 8 10 100 750 1 8 10 10 55 1 10 120 60 1 10 os 10 NENNEN NE ELE RE ENT A NID gt gt 5 lt
60. e 3 16 inch as per earlier discussion 12 02 4 5 LATERAL LENGTH IN FEET Pumps HYDRAULICS X 23 Determine the lateral diameter Using Figure X 13 3 16 inch with a perforation spacing of 2 ft Use one lateral on each side of the center feed with lateral length of 74 ft and 2 ft orifice spacing requies a lateral diameter of 2 in see Figure X 13 For 2 laterals on each side of the center feed and lateral length of 74 ft with a 3 5 ft orifice spacing allows the lateral diameters to be reduced to 1 5 in Determine number of perforations per lateral eoo 150 Using 2 ft spacing in 74 ft yields Number of perforations p x 1 74 2 1 38 perforations lateral For two laterals one on each side the total number of perforations 76 Check maximum of 6 ft2 perforation 150 ftx 3 ft 6 sq ft 75 so ok ORIFICE SPACING IN FEET Figure X 13 Graph of Lateral Length Orifice Spacing and Pipe Size for 3 16 inch Orifices 12 02 Pumps HYDRAULICS X 24 6 Determine lateral discharge rate LDR Using network pressure distal pressure of 3 5 ft and 3 16 diameter perforations Table X 2 gives a discharge rate of 0 78 gpm LDR 0 78 gpm perforation times 38 perforations 29 6 gpm 7 Determine the number of laterals This was determined in Steps 3 and 4 Use one lateral on each side of center feed so 2 laterals are required If two later
61. e C 3 1 K can be determined for any PVC pipe conforming to the above ASTM standards using the equation K 42 17 2253 Table A 3 1 Table for Constant Nominal Pipe Diameter Schedule 40 Class 200 Class 160 L1 48 65 122 9 129 4 E 4 J ju 4992 3 Friction loss for some PVC pipe fittings given in terms of equivalent length of pipe are provided in Table A 3 2 WA DOH Publication 337 009 Page 52 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 TABLE A 3 2 Friction Loss for PVC Fittings Equivalent Length of Pipe feet PVC Pipe Fittings Pipe Size 90 45 Through Through Pe Elbow Elbow Tee Run Tee Branch L 3 JL 5 0 089 20 1 2 14 17 60 4159211 WO cd 2 60 235 43 20 L 25 12 80 990 gt gt ues n L 80 1 J 9 d600 1 Lt deor 20 10 15 0 From SPEC DATA Sheet 15 Plastic Pipe and Fitting Association November 1994 WA DOH Publication 337 009 Page 53 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 A 4 MAXIMUM MANIFOLD LENGTHS Tables A 4 1 and A 4 2 can be used to determine maximum manifold lengths for various manifold diameters lateral discharge rates and lateral spacings The method used to determine the
62. e flow rate type of pipe pipe diameter and pipe length and fitings The friction loss for 40 gallons per minute in 2 inch pipe is 2 64 feet per 100 feet Note from the table that friction loss increases very rapidly as the pipe diameter decreases For example the friction loss for a 40 gpm in 177 inch diameter pipe is 8 91 feet per 100 feet Another factor is the length of the pipe and the fittings through which the effluent flows from the pump to the point of discharge The friction loss within the pressure distribution laterals is included in that design But the friction loss from the pump to the manifold must be calculated and added to the pump head requirements 12 02 Pumps HYDRAULICS X 16 In addition to straight pipe the piping system has valves elbows tees and other fittings Each of these fittings can be expressed in equivalent lengths of straight pipe A simplified way to account for these fittings is to multiply the length of the straight pipe by a factor of 1 25 Assume that the distance from the pump to the manifold of the mound is 140 feet Multiply the delivery line length by 1 25 the factor to allow for fitting losses results in a total equivalent length of 175 feet The total friction loss is 175 x 2 64 feet per 100 feet or 4 6 feet of friction loss The total head requirement for this system is 17 5 4 6 or 26 6 feet of head The pump must be selected to deliver at least 40 gallons per minute at a total dynamic
63. e program assumes that the discharge rate at the distal orifice of the last lateral in a distribution system is as listed in Table A 2 for a given orifice size at the required minimum residual head That value is multiplied by 1 1 and 1 15 to determine the maximum allowable discharge rates at the proximal orifices of the last and first laterals in the network respectively The residual head h that corresponds to those discharges was calculated by manipulating the orifice discharge equation in Appendix 2 and solving for h Using the simplified equation in Appendix A 3 the friction loss that occurs across the manifold was calculated for various materials and pipe diameters lateral discharge rates and lateral spacings L The program adds the friction loss calculated for successive pipe segments to the residual pressure which corresponds to the proximal orifice discharge at the last lateral The combined value is compared to the residual pressure at the proximal orifice of the first lateral until it is equal to or greater than this value Maximum manifold lengths were calculated as described above for various pipe materials and orifice diameters Slightly greater manifold lengths were obtained when 1 8 and 5 32 inch orifices were assumed using 5 feet residual pressure at the distal orifice see Table A 4 2 These tables were generated using Schedule 40 as the pipe material which yields the most conservative result
64. e top of the sludge and the entrance to the screening device must be 6 inches 2 4 2 6 The effluent quality discharged from a pump vault in a single compartment tank must be equal to the expectation for a separate pump chamber that WA DOH Publication 337 009 Page 17 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 receives screened effluent from a two compartment septic tank 2 4 2 7 Materials and construction must assure a watertight vessel which is resistant to corrosive attack by chemicals and conditions typical for a sewage environment 2 4 2 8 The minimum size of septic tank must be 1500 gallons as measured at the invert of the outlet In addition the lowest liquid level pump off must have a minimum of 1000 gallons and thereafter coincide with the requirements of WAC 246 272A 0232 2 5 Pumps Fittings and Controls 2 5 1 Pumps must be selected to pump effluent and be capable of meeting the minimum hydraulic flow and head requirements of the proposed on site system Additional requirements that pumps and pump installations must meet are 2 5 1 1 Pumps 2 5 1 1 1 All pumps must be installed so that they can be easily removed and or replaced from the ground surface Under no circumstances shall pump replacement and or repair require service personnel to enter the pump tank 2 5 1 1 2 All pumps must be fitted with unions valves and electrical connect
65. ecommended standards Glossary of Terms A glossary of common terms for all RS amp Gs can be found on the DOH Web site at http www doh wa gov ehp ts WW RSG Glossary 8 29 07 pdf WA DOH Publication 337 009 Page 6 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Typical RS amp G Organization Standards Section Performance Explanation How this technology is expected to perform treatment level and function Application How this technology is to be applied This section includes conditions that must be met prior to proceeding with design Topics in this section describe the approved status of the technology component listing requirements permitting installation testing and inspection requirements etc Design How this technology is to be designed and constructed includes minimum standards that must be met to obtain a permit Operation and Maintenance Appendices How this technology is to be operated and maintained includes responsibilities of various parties recommended maintenance tasks and frequency assurance measures etc Design examples figures and tables specific applications and design and installation issues WA DOH Publication 337 009 Page 7 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Introduction Pressure distribu
66. ed as they are available in many sizes e Air leaks in the siphon or fittings will prevent the siphon from functioning e If the siphon chamber fills too rapidly the bell and siphon will not receive a full dose of air and will enter a trickling mode e Adjustment to the trip level of the liquid in the siphon chamber is limited dose volume is better handled by careful sizing of the siphon chamber e Blockage of the snifter tube even momentarily at the end of the discharge cycle will cause the siphon to enter a trickling mode e Transport pipe must be vented just outside the siphon chamber and other venting must be placed in the system as needed e It is advisable not to bury the transport pipe until the system is tested and proper operation is verified additional venting may be needed for unanticipated air locks see Figures 9 and 10 2 6 Piping Materials The pipe materials must meet the following minimum specifications 2 6 1 Ata minimum the material must meet ASTM D2241 Class 160 or equivalent 2 6 2 For schedule 40 and schedule 80 PVC use ASTM D1785 2 7 Manifold See Appendix A 4 WA DOH Publication 337 009 Page 23 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 The primary function of the manifold is to deliver equal flow to all lateral orifices while minimizing system friction losses While manifold patterns may take many for
67. ed flow through the soil or filter media b Maintaining effluent in the lines will promote biological growth which will accelerate clogging of the orifices and buildup of sludge in the lines It also makes the laterals subject to freezing in areas where this is a concern WA DOH Publication 337 009 Page 59 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Appendix D Advantages Disadvantages of Siphon Dosed Systems 1 Some advantages of siphons a they do not require electricity b there are no moving parts c they can be constructed entirely of corrosion resistant material d they require very little maintenance e they do not require external controls as cycling is automatic f duplex installations can be made to alternate automatically g they can dose a remote drainfield without a large transport line to the siphon chamber h they allow the use of small pumps with low energy consumption to dose a system with high velocity requirements 2 Some drawbacks of siphons a they cannot by themselves limit the total volume discharged to the drainfield in a day and therefore cannot protect the pressure distribution component from hydraulic overload b they can go into a trickling mode and will remain there until manually recharged with air this condition does not achieve equal distribution and may destroy the receiving component c they
68. effluent in the active soil layers where microbiological and plant activity is maximized A typical application for a low pressure pipe system is shown in Figure 15 with a detail of the trench cross section Components The low pressure pipe system includes pretreatment with a septic tank or alternative system a septic tank effluent filter a pump tank including controls and pump transport line to connect the pump to the absorption field manifold and small diameter lateral pipes The pretreatment system must include an effluent filter to prevent clogging of the small diameter pipe and small holes used to distribute the flow in the absorption field The effluent filter must be cleaned every three months to assure that the system remains operational A low pressure pipe system is dependant upon the operation of several mechanical devices including the pump and 12 02 Pumps HYDRAULICS X 28 TRENCH FILL MATERIA NO COMPACTION W MIN os OF 9 MOUND 6 1 5 OR 624 PEA GRAVEL ORIFICES T LOCATED SIDE SEPTIC TANK lar HAMBER CONTROL PANEL TRANSPORT PIPE PRESSURE DISTRIBUTION MANIFOLD LATERALS PIPE Nest LEANDUT MONITORING PORTS Figure X 15 Typical Pump Tank Controls and Pipe Network Components 12 02 Pumps HYDRAULICS X 29 must be supplied with a reliable power source The pump tank configuration is shown in Figure VII 14 The system should have a visual and audible alarm to notify the h
69. essible for any service technician to cut the power to the system before any maintenance work is begun The pump tank should have a volume adequate to provide the minimum volume needed to keep the pump intake submerged the pump down volume of one pump cycle and a reserve capacity of 7596 of the daily flow in case the pump fails Most pump stations are equipped with an alarm to indicate that the water level is rising above the normal volume Once the alarm is activated the pump tank should have enough reserve to handle 7596 of the daily flow However in many situations even this reserve volume may not allow enough time to get the pump operational Some pump stations are now equipped with an additional power outlet to allow the pump tank to be pumped using a portable pump This will provide additional capacity until the pump can be repaired Most pump stations are designed so that the discharge line from the pump will drain back into the pump tank by gravity when the pump shuts off The pump used in this application must be designed to allow this drain back feature which will make the impeller turn backwards This feature will help to prevent freezing of the lines in the absorption field In addition the pump discharge line should be fitted with a quick disconnect or union so that the pump can be easily removed for repair Easy access to the pump tank for maintenance and repair is a critical factor in the design of a pump station The pump station
70. essure Distribution X 14 X 19 X 20 X 25 X 27 X 33 X 1 X 3 X 4 X 5 X 5 X 6 X 9 X 10 X 11 X 13 X 15 X 17 X 23 X 26 X 28 X 30 X 31 12 02 Pumps AnD HYDRAULICS X 1 INTRODUCTION Pumps are often utilized in onsite wastewater systems to lift wastewater for improved system location options on a site distribute effluent uniformly time dose an enhanced treatment or soil absorption system component inject air in an aerobic treatment unit ATU lift drainage water to lower a water tables Figure X 1 shows the use of a pump to lift effluent to a soil absorption area at higher elevation than the wastewater source This use allows much greater flexability in selection of the wastewater systems and its location Whenever a pump is required the maintenance and accessibility of the system are critical factors in the continued operation of the system Pump stations require careful design installation and maintenance by qualified technicians The pump equipment and controls should be located in an accessible area and be protected from weather and vandalism All components of the pumping station should be watertight and resistant to corrosion i Figure X 1 Pump Used to Lift Wastewater to a Higher Elevation than the Source PUMP APPLICATIONS Pumping raw sewage requires that the pump be designed to handle the solids found in raw wastewater This type of pump has a non clog impeller and many also have a grinder designed 12 02 P
71. essure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Timed dosing is not required for pressure distribution soil dispersal components following treatment components that are timed dosed The flow is already time dosed to the treatment component and therefore the pump chamber out of the treatment component may be demand dosed To detect extraneous flows an elapsed time meter can be used to monitor the integrity of the liner of a packed bed filter such a sand filter by comparing the volume of liquid pumped from the sand filter with the volume pumped into it Timed dosing is strongly recommended on all pressure distribution systems This type of system enhances performance reliability and protection from abuse The requirements in WAC 246 272A and the recommendations in this document are based on the need to control the size of doses to the coarser and single grained soils and treatment media Timed dosing also prevents hydraulic overload of the receiving component Usual sources of hydraulic overload are excessive water use in the facility or groundwater infiltration into the septic tank or pump chamber Timed dosing means that both the length of each dose produces gallons per dose and the interval between doses which determines the number of doses per day is controlled by a timing device whenever a dose volume is in the pump chamber The number of pump cycles should be adjustable and in
72. ffice If timed dosing is implemented then a larger tank will be required to provide surge storage Use 2 3 daily design flow for reserve capacity Select controls and alarm from products available from suppliers 12 02 Pumps HYDRAULICS X 27 Table X 5 Void Volume for Various Diameters of Schedule 40 Pipe Normal Pipe Size inches Void Volume gal ft LOW PRESSURE PIPE SYSTEM Some sites may have severe limiting factors which must be addressed by using a system such as the low pressure pipe system Common applications for low pressure pipe systems include small lot sizes shallow 50116 soils with a slow permeability rate or steep slopes The low pressure pipe system can overcome these limitations by providing uniform flow distribution alternating dosing and resting cycles and shallow trenches The effluent is distributed into the absorption with a low pressure pump system which can distribute the flow more evenly over the soil infiltrative surface The low pressure pipe system functions to dose the soil with wastewater then allow a resting period and then dose the soil again repeating this process throughout the day on a timed basis Dosing helps maintain aerobic conditions in the soil which improves treatment of the wastewater and maintains soil permeability The shallow placement of the trenches increases the vertical distance between the trench and any restrictive layer In addition the shallow depth keeps the wastewater
73. idance Effective Date July 1 2009 Contents Page C H 6 Waitin ite mee M 8 1 Performanc SC ards D 11 1 1 roi 11 1 2 Measure of PerformanCe PD TA 11 2 Application STAC ALS es i extet uS a rp QU pU nia n VEU M TD IM RE ER 13 13 PS MENS IDEE 13 PAST Pretreatment iis eset 13 15 259 Pumps Fittings and e dai n pM Mens 18 20 ES 23 2 7 EN Pp Pe 23 2 8 Lat ral nee ener ren 25 250 Minimum Design 28 2 10 Construction Record Information 29 Us r s o run MTUUT 29 3 Operation and Maintenance D 30 3 1 Eival ate 30 3 2 Eyal ate ME Eu 30 3 3 Measure Pump Run Time per Cycle and Drawdown eee 30 3 4 Test Alarms oops cuiii cs 30 3 5 Evaluate Septic Tank and Pump
74. idual pressure location and detail of access ports on the laterals detail of pump controls floats and the position of the floats an electrical wiring diagram specific to the project WA DOH Publication 337 009 Page 28 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 9 15 system parameters and calculations used by the designer to arrive at the component sizing and flow distribution shown in the design and 2 9 16 a user s manual for the pressure distribution system must be developed and provided to the homeowner and the local health department This document may be developed in conjunction with the installer and submitted with the as built information but will be the responsibility of the designer 2 10 Construction Record Information A completed construction record submission must contain at a minimum the following items 2 10 1 all the items contained in the design submittal listed above as installed identifying any changes from the approved plan 2 10 2 the measured drawdown per dose cycle 2 10 3 timer functions 2 10 4 residual pressure and or squirt height at the end of each lateral as inspected and 2 10 5 pump run time and pump time off 2 11 User s Manual The user s manual that is a part of the design submittal must contain at a minimum the following 2 11 1 diagrams of the system components 2 11 2 explanation of general s
75. ined by using Table A 3 Equivalent length for fittings should be included Equivalent lengths are found in Table A 4 2 Determine the force main diameter The force main diameter is determined from Table A 2 The number of laterals and or length of manifold should not exceed these maximums 3 Select the pressurization unit Pumps Using pump performance curves select the pump that best matches the required flow rate at the operating head Plot the pump performance curve on the system curve Then determine if the pump will produce the flow rate at the required head Do not undersize the pump It can be oversized but will be more costly 4 Determine the dose volume required The lateral pipe void volume determines the minimum dose volume The recommended dose volume is 10 times the lateral volume It is required that the system be timed dosed daily based on the design flow Small doses need to be applied however sufficient volume is needed to distribute the effluent uniformly across the network Table A 5 gives the void volume for various size pipes 5 Size the dose tank For residential applications the dose tank must be large enough to provide for a The dose volume b The dead space resulting from placement of the pump on a concrete block c A few inches of head space for floats d 24 hour reserve capacity based on 150 gallons per bedroom The pump tank must have sufficient surge capacity to allow for timed dosing See Sectio
76. inimums are a sufficient volume to handle the functions of a septic tank and to keep the pump submerged when required b surge volume to hold one day s design flow and c additional storage for emergency situations equal to 75 of the surge volume 2 4 2 2 The pump vault must 2 4 2 2 1 extract liquid from the middle of the clear zone of the septic tank 2 4 2 2 2 have integral screening or other methods to prevent solids greater than 1 8 to pass into the pump 2 4 22 3 have screening with a minimum wetted open area of 12 ft 2 4 2 2 4 beable to supply liquid to the pump as rapidly as it is discharged from the vault while keeping the pump submerged 2 4 2 2 5 perform to these specifications between normal service intervals established for the rest of the system minimum time 6 months 2 4 2 3 The pump vault must be designed and constructed to facilitate removal and maintenance of the vault screen pumps and floats 2 4 2 4 The flow rate from the pump must not exceed 30 gpm The fluctuation of the liquid level in the tank must not exceed 10 inches Larger fluctuations are allowed for emergency storage to accommodate power outages or pump failure 2 4 2 5 minimum hydraulic detention time in the tank must be 24 hours The clarified zone must be at least 10 1 2 inches with a minimum clearance of 3 inches between the bottom of the scum layer and the entrance to the screening device The minimum distance between th
77. ion discharge rate The designer must choose an operational pressure in units of feet at a distal point This is the starting point of selecting a pump and determining if the system has equal distribution 7 Determine the number of laterals and the spacing between laterals Since the criteria of 6 f orifice is the guideline the orifice spacing and laterals spacing are interrelated For absorption area widths of 3 ft one distribution pipe along the length of trench requires an orifice spacing of 2 ft For a 6 ft wide absorption area with the same configuration it would require orifice spacing of 1 ft or the system could utilize a manifold with several laterals and have better coverage Ideally the best option is to position the perforations to serve a square such as a 2 5 by 2 5 area but that may be difficult to do but a 2 by 3 is much better than a 6 by 1 area 8 Calculate the manifold size and length The manifold length is the length pipe between the outer laterals For smaller systems assume the manifold size is the same as the force main diameter since the manifold is an extension of the force main There are procedures for determining the manifold size for larger systems Table A 2 from Otis 1981 9 Determine the network discharge rate This value is used to size the pump Take the lateral discharge rate and multiply it by the number of laterals or take the perforation discharge rate and multiply it by the num
78. ions necessary for easy pump removal and repair All pumps must be protected by approved outlet baffle screens in the chamber preceding the pump chamber or by pump screens as described in previous sections In addition pumps and controls should have gas tight junction boxes or splices and have electrical disconnects as per National Electric Code appropriate for the installation The boxes should be placed so that they do not interfere with the servicing of other components 2 5 1 1 3 Pumps and electrical hook ups must conform to all state and local electrical codes 2 5 1 1 4 If any portion of the pump fittings or transport line is at a higher elevation than the drainfield the system must be equipped with an air vacuum release valve or other suitable device to avoid siphoning WA DOH Publication 337 009 Page 18 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 If a check valve is used in the system a vent hole should be installed upstream from the check valve so the pump volute impeller chamber is kept filled with effluent Some pumps may cavitate if the impeller is not kept submerged Under most circumstances this hole will be needed only when the chamber is first filled with liquid or after it has been cleaned 2 5 1 2 Pump Controls 2 5 2 1 Timed dosing is recommended whenever pressure distribution is used WAC 246 2
79. it is either desirable or required to 1 achieve uniform application of wastewater throughout the drainfield area 2 treat and dispose of effluent higher in the soil profile 3 avoid potential contamination of ground water beneath excessively permeable soils 4 improve the treatment performance and extend the life expectancy of a drainfield or other component 5 reduce the potential for breakout or seepage on slopes 6 distribute effluent to all sand filters mounds all Type 1 soils and all other soils with less than 24 inches of vertical separation Pressure distribution is also appropriate for sites in aquifer sensitive areas and for larger drainfield systems Finally in certain conditions where pumping is necessary due to elevation problems pressure distribution can be incorporated with only a little additional effort WA DOH Publication 337 009 Page 9 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 System Components Process Summary Pressure distribution systems require the following basic components septic tank or other pretreatment to the same quality as domestic septic tank effluent pump or siphon chamber or equivalent transport line manifold laterals and drainfield Figure 1 illustrates the major components of a typical pressure distribution system that are described below Component Primary Function Septi
80. ivalent to about 600 watts of power consumption The nameplate amperage on motor is typically the maximum current draw during startup which occurs very rapidly Continuous running current is often 1 2 to of the startup amperage An estimate of the pump energy use can be calculated by multiplying the current in amperage by the voltage to obtain the wattage If the running amperage is not known use of the startup amperage In this example the pump will use 600 watts x 0 29 hours 174 watt hours or 0 18 kilowatt hours per day Knowing the kilowatt hours the energy costs may be calculated using the current price per kilowatt hour Although freezing of lines has not been identified as a problem for continuous use systems Figure X 12 shows how to frost proof the lateral line in the soil absorption system The discharge piping should be sloped to drain back into the pump station as described earlier 12 02 Pumps AnD HYDRAULICS X 17 GRAS COVER vh vh we wb m LAYER OF GEOTEXTILE FABRIC FOR FOLIR INCH LAYER OF HAY OR STRAW COVERED WITH RED RESIN PAPER p IERFBRATIDN DRILLED lt iTO pem LOAMY SAND LAYER PLus MM FIELD mA PERFORATIONS LOCATED AT BOTTOM OF LATERAL CLEAN SAND LAYER ORIGINAL SOIL PROPERLY SCARIFIED BEFORE PLACING ES SAND LAYER Figure X 12 Section of Low Pr ssi to Minimize PRESSURE DISTRIBU UTION NETWORK a gt E 1 Designin E pressure distri
81. kewise maintaining the pipes full of effluent between doses will promote more rapid biological growth on the inside of the pipes and thereby promote clogging of the orifices WA DOH Publication 337 009 Page 58 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 4 Orifices in the 12 o clock Position a As mentioned above orifices in this position will maintain the laterals full or partially full and therefore reduce the amount of effluent needed to pressurize the system This feature is important when designing a system with reduced dose volumes b Orifices in the up position require the use of orifice shields or chambers to prevent blocking of some orifices with gravel pieces Shields also deflect the squirt over a wider surface area and spread the effluent over more of the infiltrative surface Shields have the greatest importance in systems with medium to coarse sand soils or with imported media providing the treatment c Maintaining effluent in the lines will promote biological growth which will accelerate clogging of the orifices and buildup of sludge and slime in the lines It also makes the laterals subject to freezing in areas where this is a concern d May be drained by putting a few orifices in the 6 00 o clock position or by draining laterals and transport line back to the surge tank However these practices will increase the dose volume required 5 Orifices
82. l Eb Miller E R D D Jones and J E Yahner Steps in Constructing b essure Distribution Septic System ID 163 Purdue University Cooperative Extension Service January 1985 Missouri Farme A eSyst Reducing the Risk of Groundwater Contamination b Improving Household Wastewater Treatment WQ680 University of Missouri Farmstead Assessment System Fact Sheet 6 October 1995 http extension missouri edu explore envqual G0680 htmi s stem Mote C R Pressurized Distribution did On M omestic Wastewater Renovation uc Department of Health of Environmental Health Office of Shellfish and Water Protection July 2007 http www doh wa gov ehp ts ww pres dist rsg 7 1 2007 pdf Wisconsin DOC Pressure Distribution Component Manual for Private Onsite Wastewater Treatment Systems SBD 10706 P N 01 01 Department of Commerce Division of Safety and Buildings January 2001 http commerce wi gov SBdocs SB PowtsManualPressureDistributionShowEdits pdf WSU Properly Managing Your Pressure Distribution System EB1673 Washington State University Cooperative Extension June 1992 Recommended Standards and Guidance for Performance Application Design and Operation amp Maintenance Pressure Distribution Systems July 2009 Washington State Department of Division He ALT Health Office of Shellfish and Water Protection Pressure Distribution Systems Recommended Standards and Gu
83. l pressure see Appendix A 2 for a discussion Table A 1 gives the maximum lateral length for each orifice diameter lateral diameter and orifice spacing WA DOH Publication 337 009 Page 43 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 1 Lateral Design Table Maximum Lateral Length ft Orifice Spacing Pipe Material Class 200 Class 160 ee dS e e Rcge IE Se a ie oe oe ea 8 986 ws me ws i5 15 e 793 ws is 2 9 96 1075 110 120 123 144 148 165 175 192 Ls poo p 3s 1005 ws 15 2 9 120 Us 120 135 140 150 156 Us 164 184 188 210 220 ie 6 20 240 246 132 141 1455 Us 160 170 176 5 1975 202 5 Us 207 222 22 248 268 276 Us 290 310 320 ws 3 360 39 3m 1 39 4 46 am o s 5 525 535m 1 1 3 l 4 1 o 60 WA DOH Publication 337 009 Page 44 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 1 Lateral Design Table continued Maximum Lateral Length ft Lateral Orifice Spacing Pipe Material Class200 Class 160 989 1 1 1 4 36 2 72 ET HU cde 85 532 1 6 7 90 96 L 9
84. laced in the 6 o clock position to facilitate draining after each pump cycle to prevent freezing in areas of the state where that may occur or to prevent build up of microbial growth inside the laterals they must have some mechanism to break the flow an orifice shield that drains a pad of gravel etc See sections on orifice size orientation and shields and Figure 7 2 8 3 Orifice Spacing To prevent excessive variations in discharge rates and possible subsequent localized hydraulic overload the maximum acceptable flow deviations stated in the Performance Testing section Section 1 2 of this document must be heeded 2 8 3 1 Sand filters including sand lined trenches mounds and pressure distribution in soil types 1 and 2 and in medium sands must have a minimum of one orifice per 6 ft of infiltrative surface area evenly distributed WA DOH Publication 337 009 Page 26 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 8 3 2 In other soil types there must be a minimum of one orifice every six feet on center along the lateral While these are minimum requirements orifices spaced at closer intervals may be prudent Closer orifice spacing should be considered when small doses are specified and where the infiltrative surface is in highly structured soils or has large macropores 2 8 3 3 The maximu
85. ll The pump can raise the level to a height of 30 feet but the flow at or above that head 1s zero At any head less than 30 feet some flow will occur For example at 25 feet of total head the discharge will be approximately 25 gallons per minute This information can be read from the graph or the table in Figure X 10 Referring to Figure X 10 the shutoff head of the 12 horsepower pump is 80 feet intersection of the pump curve with the vertical axis At 40 feet of head the pump can discharge 43 gallons per minute The pump supplier can provide a pump curve to be used to select the right pump for each application Note that even though pumps A B and C all are half horsepower each has a very different pump curve If the requirements for a system are a pump which will deliver 20 gallons per minute at 20 feet of total dynamic head none of the pumps presented in Figure X 10 will deliver precisely this specification A gate valve will need to be installed to dissipate a small amount of head so that the actual head delivered by the pump will be approximately 21 feet If the 1 2 horsepower high head pump A is used and exactly 20 gallons per minute are desired then the pump will actually deliver about 65 feet of total head 45 feet of which will be dissipated in the gate valve If the pump application is to deliver flow to a pressure distribution system in a mound for example this is a self balancing system As the flow tends to increase
86. ludge accumulation checking the operation of floats checking for signs of leaking in tank or the risers and checking the operation of alarms present in the system Low Pressure Pipe Design Example Single Family Residence Design Flow 360 gallons per day gpd Tables used in this section are from the EPA Design Manual for Onsite Wastewater Treatment and Disposal Septic Tank Two compartment septic tank witha minimum liquid volume of 1000 gallons and equipped with an effluent filter having a maximum particle size of 1 8 inch b Dosing tank with minimum of 500 gallon volume above pump intake Absorption Field a Elevation Head 15 ft from tank to highest line b Application Rate 0 2 gpd ft c Minimum Area 360 0 2 gpd f 1800 ft Pipe l inch lines 5 ft on center with 3 16 inch holes drilled 6 ft on center Dosing Rate a Based on 3 16 inch holes at 4 ft of head b Number of holes per line 60ft length 2 holes 3 ft from each end Spacing 6 ft on center 10 holes per line For 6 lines 60 holes total d Lateral lines are 1 inch schedule 40 PVC e Flow rate per hole according to Table VII 5 0 83 gpm hole 4 ft head 1 73 psi 2 31 psi ft head f Total dose rate 0 83 gpm hole x 60 holes 0 83 gpm for air vent hole 50 6 gpm g Elevation head 5 ft out of tank 15 ft to top of absorption field 20 ft Fitting Adjustment a Supply line from pump to last lateral 3
87. ly if the transport line remains full between doses When check valves are used in the manifold just downstream of each lateral the manifold and laterals too when orifices are in the 12 o clock position stays full of effluent between doses With this style 1 there is no drainback from the upper laterals and manifold into the lower lateral 2 the system is completely charged within just a second or two after the pump is turned on and 3 the system can be dosed with very small volumes per dose Note caution about check valves in section 2 7 1 of this section Cross construction See Figure 5 If the lateral orifices are drilled in the 6 o clock position this design will allow the laterals and a portion of the manifold to drain between doses assuming the transport line remains full between doses Tee to Tee with the manifold above If the lateral orifices are drilled in the 6 o clock position the entire distribution network will drain after each dose This may be desirable on a sloping site where check valves are not installed in the manifold to prevent upper laterals from draining back through the manifold to the lowermost laterals thereby overloading them If the orifices are drilled in the 12 o clock position the laterals will remain full between doses This may be desirable when the objective is to pressurize the distribution network quickly without the use of check valves Caution should be taken to minimize the potential f
88. m spacing between the outside laterals and the edge of the trench or bed must be 1 2 of the selected orifice spacing 0 5 feet 2 8 4 Orifice Shields Orifice shields may be the half pipe design the local cap type or another design which accomplishes the same end result See Figure 7 2 8 4 1 When orifices are oriented in the 12 o clock position orifice shields or gravelless chambers must be provided 2 8 4 2 The shields must be strong enough to withstand the weight of the backfill and large enough to protect the orifice from being plugged by pieces of gravel 2 8 5 Cleanouts and Monitoring Ports 2 8 5 1 All pressure distribution laterals must be equipped with cleanouts and monitoring ports at the distal ends see Figures 8A and 8B These cleanouts and monitoring ports must 2 8 5 1 1 have threaded removable caps or plugs on the ends of the laterals to allow for cleaning the laterals and for monitoring the lateral pressure 2 8 5 1 2 belarge enough to allow access to caps or plugs with hands tools etc 2 8 5 1 3 be accessible from the ground surface 2 8 5 1 4 open and slotted at the bottom and 2 8 5 1 5 be void of gravel to the infiltrative surface to allow visual monitoring of standing water in the trench or bed 2 8 5 2 All designs must show them in detail and explain how they accomplish the respective tasks The functions of monitoring and cleanout can be separated and al
89. may need to have some type of built in rail or guide to allow the pump to be easily installed or removed If the pump tank is not concrete then the tank may need to be bedded in concrete or anchored to prevent floatation when the tank is nearly empty Fiberglass and polyethylene tanks will need to h ve some type of anti floatation design incorporated into the installation of the tank Usually the manufacturer will include installation specifications designed to prevent floatation If the tank has two or more compartments at least one of the compartments should be full enough to prevent the possibility of floatation Depending upon the application the pump station may require a filter If the pumped effluent is being discharged into a soil absorption field then the pump station will usually have some type of effluent filter to keep solids out of the absorption field Filters should also be used in pump stations which are used to dose a media filter such as sand or textile filters If the pump station is using any type of high head effluent pump then a filter and pump screen are mandatory A variety of different sizes and configurations are available for these effluent filters The type of filter used will depend upon the application the tank and the type of pump being used The filter will need to be accessible for cleaning and should be designed for easy removal 12 02 Pumps HYDRAULICS X 8 PUMP TYPES Recently the grinder pump has
90. mp must operate at is the sum of a System network head 1 3 x distal pressure with minimum 2 5 feet b Elevation difference and c Friction loss in the pipe network Sizing the Pump or Siphon The effluent pumps used for pressurizing thedistribution networks are either centrifugal effluent pumps or turbine effluent pumps The turbine effluent pump which is a slightly modified well pump is relatively new to the onsite industry In comparison the centrifugal pump is a higher capacity lower head pump with a relatively flat performance curve The turbine pump is a lower capacity higher head p mp with a relatively steep performance curve Turbine pumps probably have a longer life and may be the preferred choice for timed dosing because of their longevity relative to stop starts Using pump p rformance curves select the pump that best matches the required flow rate at the operating head Plot the pump performance curve on the system curve Then determine if the pump will produce the flow rate at the required head Do not undersize the pump Care must be taken in sizing siphons The head that the network operates against has to be developed in the force main by backing up effluent in the pipe If the discharge rate out of the perforations is greater than the siphon flow rate the distal pressure in the network will not be sufficient Some manufacturers recommend that the force main be one size larger than the siphon diameter to allow the air i
91. ms the most common are the center and the end manifolds End manifolds suffice for short laterals but center manifolds allow for use of smaller lateral pipe sizes Manifold Lateral Connection The laterals can be connected to the manifold in several ways The manifold to lateral connection must be appropriate for the site conditions and the specific use Several types are described below A header manifold is positioned at an elevation below the laterals Figure 3A with check valves flow control valves and feeder lines to each lateral This configuration will maintain the manifold feeder lines and laterals full between doses will not allow drain back and can be adjusted at one location to equalize residual head in all laterals This arrangement can deliver small volumes per dose allowing many doses per day if desired Caution should be taken to minimize the potential for effluent freezing in the laterals and manifold A header manifold is placed at an elevation above the laterals Figure 3B without check valves with flow control valves and feeder lines to each lateral The measured flows from an orifice in each lateral are nearly equal without the use of check valves and without maintaining the system full between doses Tee to Tee with manifold below See Figure 4 When freezing and sloping site conditions are not a concern this method of construction can be used to allow a very rapid pressurization of the system especial
92. n E of the manual for additional information and requirements for dosing other applications 6 Select controls and alarms Select quality controls and alarms Follow electrical code for electrical connections DESIGN EXAMPLE This example will follow these steps to design a pressure distribution network for a bed system All requirements found in Section F Absorption Field Methods and Guidelines for Class I Effluent of the manual must be followed The bed absorption area is 452 ft 113 ft long by 4 ft wide The force main is 125 ft long and the elevation difference is 9 ft with three 90 elbows Central manifold distribution system will be used A Design of the distribution network Steps 1 Configuration of the network This is a narrow absorption bed on a sloping site 4 x 113 452 0 2 Determine the lateral length Use a center feed the lateral length is Lateral Length B 2 0 5 ft Where B bed absorption length 113 2 0 5 ft 56 ft 3 Determine the perforation spacing and size Perforation spacing It is recommended that each perforation covers a maximum area of 6 2 The absorption area is 4 ft wide Two laterals on each side of the center Spacing area orifice x no of laterals absorption area width 6 2 2 4 ft 3 ft Best option Ideally the best option is to position the perforations to serve a square but that may be difficult to do In this example each perforation serves
93. n the force main to escape However this will reduce the distal pressure in the network and it may drop below the design distal pressure 1 Determine the dose volume required The lateral pipe volume determines the minimum dose volume The recommended dose volume has been 5 10 times the lateral volume It has also been recommended that the system be dosed 4 times daily based on the design flow The residents do not always use the design flow and so some mounds are only dosed once a day When timed dosing is used effluent is applied a number of times per day with smaller doses However sufficient volume needs to be applied to distribute the effluent uniformly across the network Thus net dose volume is 5 times the lateral pipe volume 12 02 Pumps HYDRAULICS X 22 2 Size the dose chamber The dose chamber must be large enough to provide the following The dead space resulting from positioning the pump above the tank bottom The dose volume A few inches of head space for the alarm warning float Reserve capacity based on 100 gallons per bedroom recommended If timed dosing is selected the pump chamber or septic tank pump chamber must have sufficient surge capacity If a turbine pump is used and must be submerged there may not be enough surge capacity provided by the reserve capacity because turbine pumps are relatively tall 3 Select quality controls and alarms Follow electrical code for electrical connections Some may h
94. ne might consider using 5 32 or 3 16 diameter orifices which will allow for more orifices than if 1 4 orifices were used Spacing It is important to distribute the effluent as uniformly as possible over the system to increase effluent soil contact time and maximize treatment efficiency Typical spacing has been 30 36 but some designers have set spacing further apart to reduce pipe and pump sizes Typical spacing for beds has been 6 ft orifice J C Converse 2000 Positioning In cold climates it is essential that the laterals drain after each dose event to prevent freezing Because of the longer laterals normally encountered in mounds the orifices are typically placed downward for draining as it is much more difficult to slope the lateral toward the manifold force main because of their greater length 4 Determine the lateral pipe diameter Based on the selected perforation size and spacing Fig A 1a through A 3b should be used to select the lateral diameter Lateral diameter 1s also used to determine dose volume Fig A 5 5 Determine the number of perforations per lateral Use N p x 0 5 for center feed center manifold 1 for end fed end manifold Where N number of perforations p lateral length in feet and perforation spacing in feet Round number off to the nearest whole number 6 Determine the lateral discharge rate Based on the distal pressure selected Table A 1 gives the perforat
95. ng can also be based on 6 64 ft per orifice as is used in sand filter systems 3 Determine the perforation spacing and size The size of the perforations or orifices spacing of the orifices and the number of orifices must be matched with the flow rate to the network Typical orifice sizes are 1 4 and 3 16 with spacing of 30 36 inches See Table X 2 for orifice discharge rates for a typical range of heads 4 Determine the lateral pipediameter Select a diameter that is large enough to keep pressure losses low less than 15 percent of the operating pressure but small enough to keep costs low The lateral diameter selection is based on the hole size hole spacing and lateral length Charts have been developed to help in selecting suitable minimum lateral diameters See Table X 1 or X 3 for friction loss of Schedule 40 PVC pipe 5 Determine the number of perforations per lateral 6 Determine the lateral discharge rate discharge per orifice times number of orifices Select the pressure head to be maintained at the end of each lateral Typical distal pressure is 2 5 ft for 1 4 orifices 3 5 ft for 3 16 orifices and if smaller holes such as 1 8 is used consider using 5 ft of head The lower the operating head the more critical the friction head loss becomes to keep discharge uniform along lateral 12 02 Pumps HYDRAULICS X 19 7 Determine the number of laterals and the spacing between laterals If the 6 sq ft per orifice guideline
96. nks installed in series in order to minimize the turbulence and allow the septic tank to function properly in removing solids and scum The volume of wastewater delivered in one pump cycle should be no greater than 1 of the volume of the first compartment If two septic tanks are used in series the volume of the pump cycle may be increased to 5 the volume of the first tank PUMP CONTROLS The pump is usually controlled by floats which are suspended in the pump tank The floats may be mechanical or mercury floats and may be rated as normally on or normally off In any case the float is designed to hang vertically so that as the water level in the tank rises the float gradually becomes suspended until the water completely covers the float and it is inverted in the water When the float is inverted it will throw an electrical circuit either open or shut depending upon the wiring configuration Many pump stations have three floats a low water alarm the on off float and a high water alarm In the three float system the low water alarm float is always submerged unless the water level falls below the low water alarm level Remember that the pump intake and body of the pump must be kept submerged to provide lubrication and cooling of the pump The low water alarm will indicate abnormal conditions and alert the homeowner to a problem in the pump tank The on off float is designed to turn the pump on when the water level gets high and then
97. no capacity for flex Rubber grommets around smaller inlet and discharge pipes conduit and junction box penetrations can also be effective in controlling leaks Risers A 24 inch riser is practical when installing it over a 20 inch hatch of the septic tank because a solid foundation is needed to attach the riser to the tank If a riser is integral to the top of the tank a 20 inch riser will suffice 2 3 3 Outlet Baffle Screen Filter An outlet baffle screen or filter must meet the following performance criteria 2 3 3 protect the pressure distribution drainfield discharge orifices from plugging by particles larger than the orifices 2 3 3 2 protect the effluent pump from damage due to particles which exceed the pump s capacity to pass may be an issue with some types of pumps 2 3 3 3 perform these functions without loss of performance between routine service events 2 3 3 4 perform these functions with routine service no more frequent than that required for other system components or the system as a whole 2 3 3 5 is constructed of durable non corroding materials 2 3 3 6 draws liquid from the clear zone of the septic tank 2 3 3 7 be designed constructed and installed for easy and thorough cleaning WA DOH Publication 337 009 Page 14 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Outlet Baffle Screen Filter
98. nternal volume of the pump chamber must be sufficient to provide the daily design flow volume dead space below the pump inlet for sludge accumulation and sufficient depth to provide full time pump submergence when required An additional emergency storage volume of at least 7596 of the daily design flow is also required may include volume to flood capacity in both the pump tank and the septic tank Pump Chamber Volume For most applications an 18 inch minimum space for sludge accumulation in the pump chamber is prudent Pump chambers receiving septic tank effluent will accumulate sludge and scum and in some new systems it will form quite rapidly The sludge level will never be above the intake of the pump Emergency storage is required for periods of power outages or equipment malfunctions For systems where continuous operation and maintenance are provided by a management entity acceptable to the local health department a reduction in the volume required for reserve storage may be considered Reductions in pump chamber volume may also be considered when Duplex or redundant pumps are used 2 4 4 include a screen if one is not provided at the outlet of the septic tank See 2 3 3 for performance criteria of the screen The local health officer may allow this option only if O amp M is assured through contract with third party entity Screening at the septic tank outlet may result in a higher quality effl
99. o prevent wobble and to drill the hole perpendicular to the pipe Proper layout and control will ensure that the design number of orifices are actually placed in each lateral The above formula for calculating orifice discharge rates is recommended However the choice of coefficient to use in a design can vary from 11 79 to 16 depending on the experience of the designer in being able to predict accurately and control for the friction losses and other variables of construction and manufacture For many designers experience has shown that use of a slightly higher coefficient in the equation more accurately predicts the actual flow For whichever coefficient is selected it is critically important that the same coefficient be used throughout the design Other ways to handle the inaccuracies are to add 10 to the total flow after the calculations or to design to more than minimum residual head All of these are acceptable 2 8 1 Residual Pressure Requirements For systems with orifice diameters of 3 16 inch or larger the minimum residual head at the orifice is 2 feet 87 psi For systems with orifices less than 3 16 inch diameter the minimum residual head is 5 feet 2 18 psi 2 8 2 Orifice Size and Orientation 2 8 2 1 Orifices must be no smaller than 1 8 inches in diameter 2 8 2 2 When using gravelless chambers with pressure distribution the orifices must be oriented in the 12 o clock position If one or two orifices are p
100. o that they can be removed for servicing or replacement Unions placed at the check valve are a common means to allow servicing of the check valves while avoiding destruction or severe excavation of the manifold Some brass check valves can be disassembled without removing them from the line 2 8 Laterals See Appendix A 1 A 2 A 3 The laterals in a pressure distribution system are perhaps the most important design aspect All design considerations to this point are essentially to serve the delivery of equal flows to each square foot of drainfield bottom area Orifice Design The actual flow rate from each orifice is best represented by the equation QO 11 79 d n where Qo is the orifice flow in gallons per minute d is the orifice diameter in inches h is the discharge head in feet also called residual head see Appendix A 2 for a derivation of this equation There are other factors complicating accurate calculation of the orifice flow rate such as accurate drilling of holes class of pipe size of pipe and slight variations in the friction coefficients used for fittings Proper technique and practice in drilling holes includes use of WA DOH Publication 337 009 Page 25 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 proper drill size and a sharp bit Accurate holes also may require jigs or other drill stabilizing tools t
101. oating when the ground is saturated The pump inside the tank should be elevated above the bottom of the tank to allow for unobstructed flow into the pump intake and to prevent solids from clogging the intake or plugging orifices The pump manufacturer will provide information on how high the pump intake should be from the bottom of the tank Examples of pump tank configuration are shown in Figures X 4 X 5 and X 6 12 02 Pumps AnD HYDRAULICS X 5 BASEMENT m dd DROP BOXES AND TRENCHES TWO COMPARTMENT PuMP LOCATED SEPTIC TANK IN BASEMENT PUMPING STATIONS FOR ONSITE TR TEMS Figure X 4 Gravity Serves Ground Floor and a p ge from Basement 5 THERE PEEL N NO SEE ar Heme RIP HAKES PUT Pres Sal 2755p Caves 2 PLA TES DRAP TERE IR PPE REP PLASTEE Prc 4 MIN FROM Bottom r TRENGI HASE MENT TD WATZR TAnL oR CLAY OR LAYZR s e p TANK Figure 5 Pump Lifts Tank Effluent to a Shallow Absorption Field 12 02 Pumps AND HYDRAULICS X 6 SEPTIC TANK BASEMENT DROP BOXES OR INSPECTION PIPES SEPTIC TANK BASEMENT SUMP PUMP OR SEWAGE EJECTOR PUMP F BASEMENT STOOL DISTRIBUTION Box TOTAL TRENCH LENGTH DEPENDS ON PERCOLATION RATE AND SIZE OF HOME A D0
102. omeowner if the system is malfunctioning The laterals are usually 1 2 inch diameter schedule 40 PVC with 3 16 inch holes drilled at specified intervals The wastewater effluent travels in the transport line to the manifold which is used to feed into the laterals The best configuration for the system is shown in Figure X 16 which shows the pump tank located at the lowest elevation in the system This configuration will allow the transport pipe and the manifold to drain back into the pump tank during the rest cycle Using this configuration the discharge line from the pump should have a small weep hole which empties into the pump tank to allow the lines to drain back into the pump tank With this configuration a check valve is not needed on the transport line however the supply manifold should have a ball valve between the manifold and the lateral whichis located 6 inches above the lateral line as shown in Figure X 15 The 6 inch elevation and holes drilled below the 12 o clock position will help the laterals drain out into the drainfield and will prevent the laterals from draining back into the pump tank This configuration is commonly used on steep slopes and when freezing conditions may develop if the lines are not self draining The ball valve is used to adjust the flow so that all lines operate at the same head pressure which is needed to keep the even flow distribution Other configurations which use a check valve with a header manifold pipe or
103. or effluent freezing in the laterals Sloping Sites Manifold designs for sloping sites are particularly critical Laterals at different WA DOH Publication 337 009 Page 24 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 elevations will have different residual pressures with the lowest lateral having the highest residual In addition if the manifold is not designed correctly the lowest lateral will receive pressure before the top lateral and system backflow will continue to the lower laterals after the pumping cycle has ended In this instance the lowest trench will receive more flow than the others with the potential for overload While there may be several solutions to these problems Figures 3A amp 3B illustrate two methods for resolving them The check valves and flow control valves shown in Figure 6A and 6B are assumed to be an integral part of the manifold 2 7 1 Check Valves 2 7 1 When check valves are used they must be installed so that they can be removed for servicing or replacement This means that unions or some other fitting need to be included in the installation of check valves 2 7 1 2 The location of check valves must be well documented and marked Preferably they are located in a structure that is accessible from the surface Check valves occasionally require maintenance and therefore should be installed s
104. p dose of 150 gallons For a circular tank which is four feet in diameter the surface area is calculated as pi 3 14 times the radius squared In this case the surface area would be 3 14 x 2 12 57 square feet For foot depth in the tank there are 12 5 cubic feet 94 gallons If 150 gallons are to be pumped and the tank contains 94 gallons per foot of depth then 150 gal 94 gal ft 1 6 feet or 19 inches The start control must be 19 inches higher than the stop control in order to pump out the 150 gallons per cycle Again the drain back must also be added into the flow to provide the proper dose PUMP DISCHARGE CURVE The common submersible sump pump operates under conditions described by the characteristic pump curve The pump curve is unique for each pump at a specific operating speed and describes the head discharge relationship for the pump Four pump curves are shown in Figure X 10 as examples The total dynamic head is given on the vertical axis and the pump discharge in gallons per minute is shown on the horizontal axis As the discharge rate increases the total dynamic head a centrifugal pump can delivers will decline The point at which the characteristic curve intersects the vertical axis is the maximum head that the pump develops and is often called the shut off head The maximum head for pump C with a 1 3 horsepower as shown in Figure X 10 is 30 feet This can be visualized by thinking of a standpipe just over 30 feet ta
105. ped with an audible and visual alarm to notify the homeowner when alarm conditions exist The alarm circuit should be separate from the pump circuit so that if the pump trips the circuit breaker the alarm circuit will continue to operate Most of the control boxes have a silencer to shut off the audible alarm after the homeowner is aware of the conditions The wiring from the control box to the pump tank is usually buried and must be protected from traffic Whenever two or more residences have a common soil treatment system or if an establishment deals with the public such as a restaurant motel or school dual pumps should be installed as shown in Figure X 9 The dual pumps provide a back up to keep the system in operation during mechanical problems with one pump The dual or duplex system is similar to the single or simplex pump except that the con ontain an alternator which alternates which pump is being used The duplex system is set up so that if one pumps fai other pump will be operated to keep the system working one pump cannot keep the water level down then the oth activated while the increases and This REDW ODD CEDAR OR TREATED Post 4 4 AT LEAST 12 BELOW GRADE Ww tr a WIRE FROM POWER SUPPLY PIPE IS LAID ON A E s UNIFORM SLOPE FROM PUMP STATION
106. performance curve plotted against the pump performance curve will give a better estimate of the flow rate and total dynamic head the system will operate under 12 Select the Pump Using a performance curve from the pump manufacture the point where the flow rate intersects 60 gpm the total dynamic head 24 ft should fall under the pump curve A pump can be over sized but undersized pumps will lead to failure in performance and or longevity 4 Determine the dose volume Determine the pipe void volume from Table A 5 Use 10 times the lateral void volume Dose Volume 10 x length of lateral x number of laterals x Void volume Lateral diameter 1 5 Lateral Length 56 No of laterals 4 Void volume 0 092 gal ft 10 x 56x 0 092 206 gal dose 5 Size the dose tank The pump tank size should be based on the dose volume 24 hour storage volume and room for a block beneath the pump and control space This example is for a residential application additional information on dosing requirements can be found in Section E of the manual 6 Select controls and alarm Time Dosing The advantage of time dosing provides more frequent doses and levels out peak flows to the bed CONSTRUCTION AND MAINTENANCE Good common sense should prevail when constructing and maintaining these systems Water tight construction practices must be employed for all tanks Surface runoff must be diverted away from the system Any settling aroun
107. pid infiltration rates can lead to bacterial and viral contamination of shallow ground water especially when first put into use Therefore systems constructed in these soils should be dosed with small volumes of wastewater four or more times a day to prevent saturated conditions from occurring and hence inadequate treatment In finer textured soils saturated flow is much less likely so frequent doses do not add to the performance Large less frequent doses are more suitable in these soils to provide longer aeration times between doses EPA et al 2 5 2 Hloats or other types of liquid level sensors 2 5 2 1 For pump chambers serving single family residences the necessary floats or liquid level sensors are to actuate and turn off the pump control system and a high water alarm float Redundant off controls are optional but highly recommended and may be required by the local health officer 2 5 2 2 Commercial and multi family applications are required to meet Washington State Department of Labor and Industries requirements for Class I Division Ilocations These locations include redundant off and special ratings on installed motors and equipment 2 5 3 Siphons Siphons may be used for charging a pressure distribution system However they are flow dependent and cannot provide evenly spaced doses nor limit the daily volume See Appendix D Therefore siphons cannot be used where standard 2 5 2 1 is required unless specific
108. pumping raw sewage These pumps are classified as effluent pumps usually use a turbine type impeller They are less expensive than non clog or grinder pumps not subject to clogging because of low solids and some models are available to pump against a higher head An effluent pump may be used for a low pressure pipe system to reach an absorption area at a higher elevation for drip distribution system sand or media filter or simply to provide even distribution and or dosing of the effluent Effluent pumps usually have a screen that covers the pump intake and are located following some type of septic tank effluent filter These filters must be kept clean to allow the effluent to enter the pump intake Most of these pumps are designed to use water as a lubricant and coolant so the pump must not be operated under dry conditions If the screens are plugged and water cannot enter the intake the pump may be damaged When an effluent pump is used to deliver to a conventional absorption field flow may discharge to a drop box as shown in Figure X 2 On a sloping as shown in Figure X 1 water that upper laterals can not absorb overflows via drop boxes shown in Figure X 3 to lower laterals In designing the drop box system the invert bottom of the discharge pipe from the pump must be at least 2 inches higher than the elevation of the supply line to the next drop box This arrangement will allow water in the discharge pipe to drain back to the pump tank
109. ratories UL or equivalent 2 5 1 2 8 Other standards that engineers designers and installers need to be aware of and comply with are electrical standards for pump and control systems established by Washington State Department of Labor and Industries A control box or panel installed on a treated 4 X 4 post is acceptable practice and does not produce irritating resonations for the building occupants as occurs when the control panel is mounted on buildings 2 5 1 2 9 Minimum Dose Frequency The minimum dosing frequency must be according to the following WA DOH Publication 337 009 Page 21 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Soil Type 1 and 2 4 times per day Soil Type 3 4 times per day Soil Types 4 6 1 to 2 times per day Dose Frequency Although this standard lists the minimum frequency for various soil types more frequent doses than the minimum recommendation may be desirable in some designs Dosing of drainfields provides intermittent aeration to the infiltrative surface With this method periods of loading are followed by periods of resting with cycle intervals ranging from hours to a day or more The resting phase should be sufficiently long to allow the system to drain and expose the infiltrative surface to air which encourages degradation of the clogging materials by aerobic bacteria In sands however the ra
110. re to start testing with the pump chamber mostly full and to set off time temporarily to minutes or seconds 3 Verify that the timer off time is the same as that specified in the plan or will dose the system the correct number of times a day Check this number in minutes and note the off time One can verify activation levels by use of lights on timer For instance if the drainfield is to receive 4 doses per day the off time should be approximately 6 hours 4 Verify that high water alarm does not turn the pump on If high water alarm turns the pump on the system will not be approved Timed dose systems only Verify that the system will dose the correct number of times per day and that no float in the system turns the pump on independent of the timer A system with a timer override float will not be approved If problems are discovered during the functional testing first contact the designer or engineer If the wiring needs adjustment the electrician should be contacted In preparation for Health District final inspection fill the pump chamber An additional test for equal distribution which takes into consideration draindown after the pressure cycle is described here However it is somewhat tedious For systems with laterals WA DOH Publication 337 009 Page 12 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 having more than 18 inches difference in ele
111. s shorter manifold lengths WA DOH Publication 337 009 Page 54 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Table A 4 1 for orifice diameters of 3 16 in and up with minimum 2 feet of residual head Maximum Manifold Length ft Lateral Discharge Manifold Diameter inches Rate emer Manifold EISTSTSTETRE e Te TS TSTSTSTREZ TS 4 TS T STE oo gt oo 95 N N gt N gt nN nN nN oo DID HA A A SA A A A 00 BR DID IO o ON JON ON ON JON JON WO SO JOD B B NIN R2 IY JH HY A IB 02 02 092 99 99 09 G ON ON ON 00 00 00 00 OO OO N 95 A oo Instructions This Table can be used to determine maximum length of a given diameter manifold or to determine required minimum diameter for a given manifold length Known values must include 1 Manifold lateral configuration end or central 2 Lateral discharge rate in gallons per minute 3 Lateral spacing in feet Example A Central manifold configura
112. so be accomplished in other ways WA DOH Publication 337 009 Page 27 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 8 6 2 8 2 8 2 8 2 8 Trenches 6 1 Ina pressure drainfield as in any drainfield the bottom of the trench must be level 0 5 inches 6 2 The bottom and sides of the trench must not be smeared 6 3 In gravel filled trenches and beds an acceptable geotextile must be used on top of the gravel before backfilling 6 4 sloping sites the trenches and laterals must run parallel to the natural ground contours 2 9 Minimum Design Submittal A completed design must include the following as a minimum 2 9 1 2 9 2 2 9 3 2 9 4 2 9 5 2 9 6 2 97 2 9 8 2 9 9 2 9 10 2 9 11 2 9 12 2 9 13 2 9 14 meeting all requirements of WAC 246 272 0200 daily design flow septic tank size location and outlet invert elevation pump pickup elevation and location or siphon invert elevation and location size of pump or siphon chamber transport line length location highest elevation and diameter all valves or other such components in the system manifold diameter location length and orientation lateral diameter location length orientation and elevations orifice diameter spacing and orientation dose volume pumping rate gpm dose frequency and design res
113. sses through plastic fittings in terms of equivalent lengths of pipe Sump and Sewage Pump Manufacturers 1998 Nominal size fitting and pipe Type of Fitting 90 Elbow 45 Elbow STD Tee Diversion Check Valve Coupling Quick Disconnect Gate Valve Table A 5 1 1 2 7 0 8 0 9 0 3 0 3 0 4 0 7 0 9 0 11 0 11 0 13 0 17 0 1 0 1 0 2 0 0 9 1 1 1 4 Void volume for various diameter pipes Nominal Pipe Size In Void Volume gal ft 12 350 325 300 0 5 1 1 5 2 2 5 Orifice Spacing in Feet Fig A 1a Minimum lateral diameter based on orifice spacing for 1 8 in diameter orifices Wisc Dept Of Commerce 1999 13 Lateral Length In Feet 2 5 3 3 5 4 4 5 5 Orifice Spacing In Feet Fig A 1b Minimum lateral diameter based on orifice spacing for 1 8 in diameter orifices Wisc Dept Of Commerce 1999 14 200 221 240 180 te A 2 2 E ugue OOO OZ o ooe E ami CSS V eamm 20 00 5 1 1 5 2 2 5 Orifice Spacing In Feet Fig A 2a Minimum lateral diameter based on orifice spacing for 5 32 in diameter orifices Wisc Dept Of Commerce 1999 15 P 3 3 5 4 4 5 5 Orifice Spacing In Feet Fig A 2b Minimum lateral diameter based on orifice spacing for 5 32 in diameter orifices Wisc Dept Of Commerce 1999 16 Lateral Length In Feet 350 325 300 275 250 22b 2 5 3 3 5 4 4 5 5 Orifice Spacing In
114. table values is described below Pressurized distribution systems are designed to assure even distribution of effluent throughout the drainfield area Even distribution maximizes the treatment capabilities and useful life of the absorption area Completely uniform distribution is difficult or impossible to obtain because of friction losses that occur in all piping networks so we settle for a standard or acceptable variance in orifice discharges throughout the network The maximum lateral lengths in Table A 1 were developed to assure there will be no more than a 10 variance drop in the discharge rates between the proximal and distal orifices in any given lateral The maximum manifold lengths in the tables below were developed to assure there will be no more than a 1546 variance in discharge rates between any two orifices in a given distribution system Two assumptions used to develop these tables are 1 the maximum variance in orifice discharge rates within a network occurs between the proximal orifice in the first lateral connected to a manifold and the distal orifice on the last lateral connected to the manifold and 2 the friction loss that occurs between the proximal orifice of a lateral and the point where the lateral connects to the manifold is negligible Using the assumptions mentioned above a computer program was developed to calculate maximum manifold lengths for various manifold diameters lateral discharge rates and lateral spacings Th
115. tate Recommended Standards and Guidance for On site Sewage System Tanks Until sewage tank rules are available all septic tanks must also 2 3 2 1 be watertight to a level above any possible seasonal ground water The local health officer may require leak testing 2 3 2 2 include screening of the effluent unless the screening is around the pump 2 3 2 3 have service access manholes and monitoring ports for the inlet and outlet WA DOH Publication 337 009 Page 13 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Septic Tank See Figure 2 Watertightness Some or all of the following materials can be used to aid in achieving water tightness of the tanks Use caste in place flexible rubber gaskets in the inlet and outlet openings using stainless steel clamps to seal the rubber to the pipes Use of flexible rubber gaskets sealed to the inlet and outlet openings with a ratcheted expansion seal and using stainless steel clamps to seal the rubber to the pipes Use of expanding grout material as a means of sealing tanks and risers Some grouts will shrink and crack over time and thus allow tanks to leak well after the tank is backfilled Bentonite backfill around the tank seams and pipe entrances may help provide a water tight tank Epoxy is another effective method of sealing some kinds of joints but the weather conditions must be ideal and there is
116. tewater enters the system through 4 perforated pipe The pipe does not distribute the effluent uniformly but concentrates it in several areas of the absorption unit Dosing is defined as pumping or siphoning a large quantity of effluent into the 4 inch perforated pipe for distribution within the soil absorption area It does not give uniform distribution but does spread the effluent over a larger area than does gravity flow Uniform distribution known as pressure distribution distributes the effluent somewhat uniformly throughout the absorption area This is accomplished by pressurizing relatively small diameter pipes containing small diameter perforations spaced uniformly throughout the network and matching a pump to the network This material has been extracted and modified from a paper entitled Design of Pressure Distribution Networks for Septic Tank Soil Absorption Systems by Otis 1981 It also includes material from the Pressure Distribution Component Manual for Private Onsite Wastewater Treatment Systems by the State of Wisconsin Department of Commerce 1999 Design Procedure The design procedure is divided into two sections The first part consists of sizing the distribution network which distributes the effluent in the aggregate and consists of the laterals perforations and manifold The second part consists of sizing the force main pump dose chamber and suitable controls A Design of the Distribution Network Steps 1
117. tion lateral discharge Q 40 gpm lateral spacing 6 ft manifold diameter 4 inch Maximum length 12 ft Example B End manifold configuration lateral discharge Q 30 gpm lateral spacing 6 ft manifold length 18 ft Minimum diameter 3 inch WA DOH Publication 337 009 Page 55 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 TABLE A 4 2 for orifice diameters of 1 8 in and 5 32 in with minimum 5 feet of residual head Maximum Manifold Length ft Lateral Discharge Manifold Diameter inches Rate YA ES Lateral Spacing Mani n ENN a ATEN EVE TX ENA OI IY NY HY NIN S gt ID Oo OI W W JON JON ON ON AD gt DID ID ID ID ID OO 00 OO OO DW JO OO OO ON ON O NO JO JO o N 95 AB ON nN nN Instructions This Table can be used to determine maximum length of a given diameter manifold or to determine required minimum diameter for a given manifold length Known values must include 1 Manifold lateral configuration end or central 2 Later
118. tion applies effluent uniformly over the entire absorption area such that each square foot of bottom area receives approximately the same amount per dose at a rate less than the saturated hydraulic conductivity of the soil This process promotes soil treatment performance by maintaining vertical unsaturated flow and also reduces the degree of clogging in finer textured soils Pressure distribution closely approaches uniform distribution See guidance section below A pressure distribution system consists of a pretreatment component to separate the major solid materials from the liquid a screening device to protect the pump and distribution lateral orifices from solids and a means to deliver specified doses of effluent under pressure to the distribution system Converse 1974 Converse et al 1975 Otis et al 1978 The distribution system consists of small 1 to 2 inch diameter laterals with small discharge orifices A pressure head is created within the laterals usually by means of a pump or siphon Pressure distribution is applicable to any system which uses soil as a treatment medium and may improve long term performance of those systems It is required by WAC 246 2724 for certain site and soil conditions and for high daily design flows Pressure distribution is also a required component for mounds sand filters and sand lined trenches and beds Research evidence indicates that wastewater traveling vertically through 2 4 feet of
119. to turn the pump off when the water level returns to the normal operating level The high water alarm is activated when the water level gets high and should be set to provide additional reserve capacity in the event of pump failure Examples of the float configuration for a pump station are shown in Figure X 7 where the control box is attached to the house exterior and Figure X 8 where the control box is remote 12 02 Pumps AnD HYDRAULICS X 9 Please note that the floats should be tethered to a rigid float tree which is mounted in the tank The floats should be on a short tether and must be carefully set so that they do not become tangled up with each other or come to rest on the top of any surface especially the pump casing inside the tank The most common problem encountered with these systems is that the floats are hung up and not able to work properly Also the vertical location of the pumps must be carefully set up to provide the proper dose volume per cycle to protect the pump with the low water alarm and to notify the homeowner when high water conditions exist Setting the floats at the proper height and configuration should be done by a qualified installer Some pumping stations may be equipped with a timer to operate the on off cycle of the pump These pump stations are designed to provide a specific dose at a given time interval This type of configuration is commonly used for dosing media fixed film treatment s
120. uent than screening around the pump as the flow rate through a septic tank baffle screen is much lower than through a screen around the pump However large pump chambers can continue to accumulate screenable solids as it is still a biologically active fluid Therefore it should be assumed that septic tank effluent once screened can still produce sludge and scum in the pump chamber A pump screen designed to fulfill the performance requirements and to prevent collapsing between service intervals may be a wise choice either by itself or in conjunction with a septic tank effluent filter However some pumpers insist that screens in pump chambers are a bad idea and cause many maintenance problems WA DOH Publication 337 009 Page 16 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 4 2 Pump Vault System in a Single Compartment Septic Tank Septic tanks in Washington must have two compartments However an exception to this is where a pump vault is used in a single compartment septic tank In addition to meeting all the requirements for pressure distribution systems with a separate pump chamber there are additional criteria and limitations when using this combination of septic tank and pump vault They are listed below 2 4 2 1 The minimum storage and pump working volumes in the septic tank must be equivalent to a septic tank with a separate pump chamber The m
121. umps HYDRAULICS X 2 to grind up tough and stringy solids such as a rag or wet strength towels to avoid clogging the pump Common applications for pumping raw sewage are when a lagoon is at a higher elevation or plumbing fixtures in a basement must be lifted up to the septic tank placed at the preferred shallow depth A grinder pump might typically be chosen to handle all of the household sewage to pressurize or lift to a higher level A non clog sewage pump might be selected to serve fixtures in the basement such as a bath and laundry These types of pumps are expensive and require frequent maintenance to meet service requirements In addition these pumps are typically low head so are designed for a limited lift or head of the wastewater The vertical distance from the lowest water level at the pump to the highest point of the discharge is called lift or head usually measured in feet The cost to pump wastewater against high heads can become quite expensive However lifts of 10 to 20 feet with an efficient pump will be a modest price Most onsite wastewater systems are designed to minimize the head required forthe pump in order to keep the cost for the pump and its operation reasonable The most common type of pumping situation for onsite wastewater systems involves pumping the septic tank effluent after the solids have been removed and the effluent screened For this application the capacity to handle solids is not nearly as important as when
122. utlet baffle screen Clean each time it is inspected or as needed to avoid clogging 3 5 3 forsigns of leaking in tanks and risers Repair or replace if necessary 3 5 4 for risers and lids being above grade and having lids that are secure 3 5 5 for properly functioning of floats Movement should not be restricted Floats should be positioned correctly and provide positive instrumentation signals Adjust and repair as necessary 3 6 Findings and Repairs All findings and repairs are to be recorded records filed for ready access and reports sent to local health department WA DOH Publication 337 009 Page 31 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 Figures SEPTIC TANK ACCESS RISER PUMP CHAMBER TRANSPORT PIPE ar Me a 4 SAY MANIFOLD PIPE 3 K CONTROL PANEL PRESSURE DISTRIBUTION LATERALS N CLEANOUT MONTIORING PORTS PRESSURE DISTRIBUTION DRAINFIELD WA DOH Publication 337 009 FIGURE 1 Page 32 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 FROM SEWAGE SOURCE FINISH GRADE FROM SEPTIC TANK HIGH WATER ALARM LEVEL NORMAL TIMER OFF LEVEL SECURED LID WITH GAS TIGHT SEAL 24 DIAMETER ACCESS RISER C FINISH GRADE Eo ey L J _ TO PUMP CHAMBER FLOATING MAT APPROVED EFFLUENT
123. vation the volume of liquid from an orifice same size as the others in the laterals placed in a plug or cap in the end of each lateral can be collected from a complete cycle and measured The variation between the largest volume and the least volume collected must not be more than 1596 Use of manifold designs shown in Figures 6A and 6B will eliminate significant drainback Determination of float activation level in water may take several tries For both system types note pump run time that delivers proper dose Record the results 2 Application Standards 2 1 Listing Pressure distribution is a public domain distribution technology but it does not appear on the department s List of Registered On site Treatment and Distribution Products It may be permitted by local health officers as a public domain pressure distribution system WAC 246 2724 0010 as long as there is departmental RS amp G for this technology 2 2 Permitting Installation permits and if required operational permits must be obtained from the appropriate local health officer prior to installation and use 2 3 Pretreatment 2 3 A pressure distribution system must be preceded by a properly sized two compartment septic tank with effluent baffle screen see 2 3 3 Exception see 2 4 2 2 3 2 Septic Tank The septic tank must be designed in compliance with Washington State On Site Sewage System Regulations WAC 246 272A 0232 and with the Washington S
124. ymposium on Individual and Small Community Sewage Systems ASAE Joseph MI 49085 Machmeier R E and J L Anderson 1988 Flow distribution by gravity flow in perforated pipe In On site Wastewater Treatment Proceedings of the Fifth National Symposium on Individual and Small Community Sewage Systems ASE Joseph MI 49085 Otis R J 1981 Design of pressure distribution networks for septic tank soil absorption systems Small Scale Waste Management Project 345 King Hall University of Wisconsin Madison 1525 Linden Drive Madison WI 53706 Publication No 9 6 Sump and Sewage Pump Manufacturers Association 1998 Recommended guidelines for sizing effluent pumps P O Box 647 Northbrook 600065 0647 Wisconsin Administrative Code 1999 Pressure distribution component manual for private onsite wastewater treatment systems Department of Commerce Safety and Building Division Madison WI 2
125. ystem function operational expectations owner responsibility etc 2 11 3 specifications of all electrical and mechanical components installed occasionally components other than those specified on the plans are used 2 11 4 names and telephone numbers of the system designer local health jurisdiction component manufacturers supplier installer and or the management entity to be contacted in the event of a failure 2 11 5 information on the periodic maintenance requirements of the various components of the sewage system and 2 11 6 information on trouble shooting common operational problems that might occur This information should be as detailed and complete as needed to assist WA DOH Publication 337 009 Page 29 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 the system owner to make accurate decisions about when and how to attempt corrections of operational problems and when to call for professional assistance 3 Operation and Maintenance The systems must be monitored and maintained at a frequency commensurate with the site soil system complexity and use patterns As a minimum it is strongly recommended that the items in 3 1 3 5 be inspected at six months and then yearly after the system is put into use The local health department permit should clearly delineate who must perform the inspections Refer to the system construction record for initial re
126. ystem or for a media filter such as sand or textile filter These syste ha and high water alarms but the on off cycle is controlled by the timer The tim locate ontrol box and may have to be adjusted to provide the proper dose Adjustin 1 ystems must be done by a qualified technician who understands how the ti for the pump station must be waterproof and corrosion resistant The mounted in a protected area near the pump tank The control pa in sight of the pump tank to facilitate service on the unit All electrical conne ight and in accordance with local electrical codes The control box sh m mounted MANHOLE COVER SECURED TO PREVENT UNAUTHORIZED ENTRY UNION OR OTHER Quick DISCONNECT FITTING PIPE 15 LAID ON 9 UNIFORM SLOPE FROM PUMP STATION UP TO SOIL TREATMENT AREA FOR PROPER DRAINBCK TANKI 4 PLASTIC ROPE OR LL WEEP HOLE CHAIN WITH ANCHOR RESERVE CAPACITY AFTER ALARM SOUNDS ALARM FLOAT ON SEPARATE ELECTRIGALGIRGUIT START LEVEL PUMPABLE CAPACITY AT LEAST 75 GALLONS SHuT OFF LEVEL NOTE KEEP PUMP MOTOR COVERED 12 18 MINIMUM DEPTH Figure X 7 Section of Pump Tank Showing Pump Wiring and Float Locations 12 02 Pumps HYDRAULICS X 10 permanently in the box The control box should contain an electrical shut off to allow the service provider to cut the power to the system The control box should also be equip
127. zone of the septic tank the zone between 4096 down from the top of the liquid and 4096 up from the bottom of the tank this relates to performance and service interval as well as general septic tank performance Be capped covered or otherwise constructed to prevent scum or other floatable solids from discharging from the tank by bypassing the screen or filter this relates to product performance Other specifications may be used to meet the outlet baffle screen filter performance 2 4 Pump Chamber 2 4 Pump Chamber Requirements All pump chambers must be structurally sound and conform to Washington State On Site Sewage System Regulations WAC 246 272A and with the Washington State Recommended Standards and Guidance for On site Sewage System Tanks Until sewage tank rules are available all pump chambers must also 2 4 1 1 be water tight to a level above any possible seasonal ground water Leak testing may be required WA DOH Publication 337 009 Page 15 of 61 Pressure Distribution Systems Recommended Standards and Guidance Effective Date July 1 2009 2 4 1 2 all pump chambers must be equipped with a twenty four 24 inch minimum diameter water tight riser with a secured lid that extends to the ground surface Lids must be equipped with an airtight gasket to eliminate nuisance odors and be secured from accidental or intention removal by unauthorized persons especially children 2 4 1 3 the i

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