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(A) Standards for a subsurface drip irrigation system: <br /> (1) Minimum 140 mesh (115 micron) filter with a capacity of 25 gallons <br /> per minute, or equivalent, filtration, sized appropriately to maintain the <br /> filtration rate, shall be used. The filter back -wash and flush discharge <br /> shall be caught, contained and disposed of to the sewer system, septic <br /> tank, or with approval of the authority having jurisdiction, a separate <br /> mini -leach field sized to accept all the back wash and flush discharge <br /> water. Filter backwash water and flush water shall not be used for any <br /> purpose. Sanitary procedures shall be followed when handling filter <br /> back -wash and flush discharge of gray water. <br /> (2) Emitters shall have a minimum flow path of 1200 microns and shall <br /> have a coefficient of manufacturing variation (Cv) of no more than <br /> seven percent. Irrigation system design shall be such that the emitter <br /> flow variation shall not exceed plus or minus ten percent. Emitters <br /> shall be recommended by the manufacture for subsurface use and gray <br /> water use, and shall have demonstrated resistance to root intrusion. <br /> (3) Each irrigation zone shall be designed to include no less than the <br /> number of emitters specified in Table 16 -3, or through a procedure <br /> designated by the Health Officer. Minimum spacing between emitters <br /> is 14 inches in any direction. <br /> (4) The system design shall provide user controls, such as valves, switches, <br /> timers, and other controllers as appropriate, to rotate the distribution of <br /> gray water between irrigation zones. <br /> (5) All drip irrigation supply lines shall be polyethylene tubing or PVC <br /> class 200 pipe or better and schedule 40 fittings. All joints shall be <br /> properly solvent- cemented, inspected and pressure tested at 40 psi, and <br /> shown to be drip tight for five minutes, before burial. All supply lines <br /> will be buried at least eight inches deep. Drip feeder lines can be poly <br /> or flexible PVC tubing and shall be covered to a minimum depth of <br /> nine inches. <br /> (6) Where pressure at the discharge side of the pump exceeds 20 pounds <br /> per square inch (psi), a pressure reducing valve able to maintain <br /> downstream pressure no greater than 20 psi shall be installed <br /> downstream from the pump and before any emission device. <br /> (7) Each irrigation zone shall include a flush valve /anti - siphon valve to <br /> prevent back siphonage of water and soil. <br /> 10 <br />