Section Env-Ws 373.25 - Water Pressure; Distribution System(a) Where operational pressure is anticipated to be less than 30 pounds per square inch(psi), the service line shall be oversized so as to reduce frictional losses.(b) Maximum system pressure shall be 100 psi. Any portion of the water distribution piping system where pressure is expected to exceed 100 psi shall have pressure reducing valves installed on each individual water service line 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. The water system shall maintain all pressure reducing devices.(c) For non-community water systems serving campgrounds, the following shall apply:(1) The water distribution piping system shall be capable of passing peak flow without excessive frictional loss, such that at peak flow, pressure at each lot or site shall be at least 20 psi;(2) Consideration shall be given to possible future expansion in the sizing and layout of the proposed water distribution piping system;(3) The water distribution piping system 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;(4) The spacing for on-line gate valves installed on water mains shall not exceed every 1,500 feet, and gate valves shall be provided at all intersecting pipes;(5) Blow-offs shall be installed to allow flushing of the water distribution piping system near the ends of the water mains, and shall be sized so as to permit high velocities, at least 2.5 feet per second, to be developed in the water distribution piping;(6) Where possible, dead-end piping shall be avoided. 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;(7) Water distribution piping shall be bedded in sand or other appropriate material with a minimum cover of not less than 5 feet for year-round systems;(8) Piping and valving material and installation techniques shall conform with the appropriate American Water Works Association (AWWA) specification, in accordance with Env-Ws 307, for that type of piping material where such specification exists. Where such specification does not exist for the size pipe specified in the system design, the minimum pressure rating for piping shall be 200 psi and the piping shall meet the manufacturing requirements of the American Society of Testing and Materials (ASTM) specification 2241; and(9) 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.(d) Subject to (e), below, if a water main and sewer pipe are to be installed adjacent to one another, a minimum horizontal separation of 10 feet shall be maintained.(e) When conditions prevent 10 feet of separation, the following shall be considered by the water system: (1) Where other utilities or obstacles, not including bedrock, prevent such separation, a waiver may be requested to allow location of the sewer pipe not less than 3 feet from a water main horizontally, provided that the water main is 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) If a water main shall cross a sewer pipe, the water main shall cross above the sewer pipe, with not less than 18 inches of clear separation;(3) Water piping may cross under sewer piping only when this is demonstrated to be unavoidable and only when granted by specific waiver. Special construction, including use of ductile iron water and sewer pipe, no pipe joints within 9 feet of the crossing points, and minimum 18 inches clearance shall be required; and(4) Technical criteria supporting a waiver of sewer pipe and water main separation criteria shall include:a. The topography of the area; andb. The number of utility interferences.(f) Other utilities, including, but not limited to natural gas, storm drainage, electric, telephone, steam, and cable television, shall not be installed within 3 feet of water mains.(g) On-line 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.(h) Rigid connections shall not be used to construct or repair water distribution piping systems.N.H. Code Admin. R. Env-Ws 373.25
(See Revision Note at chapter heading for Env-Ws 300); ss by #8499, eff 11-30-05