1. (a) Subject to (c) below, the system shall be designed to maintain a minimum pressure of 20 pounds per square inch (psi) at ground level at all points in the distribution system under all conditions of flow. The normal working pressure shall be approximately 60 to 80 psi and shall not be less than 35 psi.
2. (b) Subject to (c) below, when static pressure exceeds 100 psi pressure reducing devices shall be installed on each individual water service line at the meter or on the water main to maintain pressure at less than 100 psi. Any bypass line around a water main pressure reducer shall also have a pressure reducer. Where pressure reducers are installed below ground, they shall be located in a vault, which shall have a gravity drain to daylight with a rodent screen. The PWS owner shall maintain all pressure reducing devices, whether on individual water service lines or on water mains, in proper working order.
3. (c) Pressure shall be measured at ground level including at service connections up to building entrances.
4. (d) Individual booster pumps shall not be allowed for any individual residential service from the public water supply mains.
5. (e) The water distribution piping shall be so valved as to allow isolation of major sections of the water distribution piping system for repairs while still providing service to most of the water system.
6. (f) The spacing for inline isolation valves installed on water mains shall not exceed every 800 feet. Isolation valves shall be provided at all intersecting pipes. Isolation valves shall be located at not more than 500-foot intervals in areas where the ground elevation is below the flood hazard elevation as determined in accordance with Env-Dw 406.06(b) and in areas where water pipes are at a reasonable risk of being damaged by erosion.
7. (g) Blow-offs or similar flushing devices shall be installed to allow flushing of all water mains in the water distribution piping system. Flushing devices shall be sized to provide flows which will give a velocity of at least 3.0 feet per second in the water main being flushed. Blow-offs and flushing devices shall not have drains, or the drains shall be plugged, to prevent cross contamination.
8. (h) Dead-end piping shall be minimized. Dead-end mains shall be equipped with a means to provide adequate flushing in accordance with (g) above.
9. (i) Near the temporary end of a water main, a gate valve shall be installed to allow future piping extension without shutting down the system or jeopardizing the health of existing consumers.
10. (j) Water distribution piping shall be bedded in sand or other appropriate material in accordance with the applicable standard of AWWA as listed in Env-Dw 402.
11. (k) Water distribution piping for year-round PWSs shall be buried below the frost line.
12. (l) Subject to (n), below, a minimum horizontal separation of 10 feet shall be maintained between water mains and gravity sanitary or storm sewers, sewer force mains, sewer manholes, inlets, and other structures, septic tanks, and subsurface treatment systems. The distance shall be measured from outside edge to outside edge.
13. (m) Subject to (n) below, if a water main must cross a gravity sanitary or storm sewer pipe or force main, the water main shall cross above the sewer pipe with not less than 18 inches of clear separation. At crossings, one full length of water pipe shall be located so both joints will be as far from the sewer as possible. Special structural support for the water and sewer pipes shall be provided as necessary.

14. (n) When conditions prevent the minimum separation distances specified in (l) and (m) above, or when it is impracticable to install water mains above sanitary or storm sewer pipes, deviations from the requirements of (l) and (m) above shall only be allowed if a specific waiver is granted by the department in accordance with Env-Dw 406.31. In addition to any other condition(s) imposed by the department in granting the waiver, the following requirements shall apply be considered by the water system:

    1. (1) The water main shall be laid in a separate trench or on an undisturbed earth shelf located on one side of the sewer and at an elevation so the bottom of the water main is at least 18 inches above the top of the sewer pipe;
    2. (2) The sanitary or storm sewer pipe materials shall be pressure rated, and the manholes, inlets, and other sewer structures shall be watertight and shall be pressure or leak tested to demonstrate watertightness; and
    3. (3) Where water piping crosses under sanitary or storm sewer piping, a minimum of 18 inches clearance shall be required.
15. (o) When pipes cross water bodies 15 feet or wider, pipes shall be buried at least 5 feet below the water body’s bed, and isolation valves shall be installed on each side of the water body, between the water body and the first service connection.
16. (p) Piping and valving material and installation techniques shall conform with the appropriate AWWA specification, in accordance with Env-Dw 402.
17. (q) Other utilities, including, but not limited to natural gas, electric, telephone, steam, and cable television, shall not be installed within 3 feet of water mains.
18. (r) All buried non-metallic piping shall be backfilled with an effective metal tracing element located above the pipe approximately 6 inches below the finished grade.
19. (s) Gate valves and service shut-offs shall be equipped with cast iron gate box extensions. Gate valve boxes shall have cast iron covers clearly marked by the word “water” or other appropriate water supply marking and shall be installed flush with the finished grade.
20. (t) Rigid connections shall not be used to construct or repair water distribution piping systems.
21. (u) The distribution system shall not include any fixture which incorporates a stop and waste valve cross-connection, unless a reduced pressure backflow device or air gap is used pursuant to Env-Dw 505.
22. (v) Any PWS that conducts a partial or full replacement of a lead service line or galvanized service line requiring replacement is subject to the requirements of 40 CFR 141 Subpart I.
23. (w) Handling and disposal of lead pipe, galvanized pipe that might contain lead, or other lead components is subject to Env-Hw 400, Env-Hw 500, Env-Hw 800, and Env-Hw 1200.
24. (x) Where it is not practicable to bury a service line below the frost line all the way to the building entrance, for example under mobile homes, heat tape shall be installed to prevent the service line from freezing. The length of above-ground service pipe shall be minimized.

Source. (See Revision Note at part heading for Env-Dw 406) #10613, eff 6-1-14; ss by #14158, eff 12-25-24 (formerly Env-Dw 406.25)