A. Water main diameter. The minimum size of water main for providing fire protection, consumption for both domestic and commercial use shall be 8 inches in diameter. Larger size mains shall be provided where necessary to allow the withdrawal of the required fire flow while maintaining the minimum residual pressure of 20 PSI at ground level at all points in the distribution system under all conditions of flow.
B. Dead ends shall be minimized by looping of all mains whenever practical. Dead end mains in excess of 600 feet shall not be allowed.
C. Small mains. Any departure from minimum pipe size requirements must be justified by hydraulic analysis, future water use, and be considered only in special circumstances with the approval of the Water Department.
D. Cross connections and interconnections. There shall be no connections between a public water supply and any non-potable water source unless the public water system is protected by a method meeting the requirements of the State of New Hampshire Department of Environmental Services Rules and Regulations relative to cross connection control.
E. Separation of Water Mains and Underground Utilities. Other utilities crossing water mains shall cross at or near a perpendicular. There shall be an 8 inch minimum clear vertical dimension and a 4 foot minimum clear horizontal dimension each side between water mains and any other utility pipe, conduit or wire.
F. Valve Locations and Spacing. Sufficient valves shall be provided on water mains so that inconvenience and sanitary hazards will be minimized during repairs. Main valves shall be located at not more than 700-foot intervals. Water main intersections shall be valved each way.
G. Hydrant Location and Spacing. Hydrants shall be provided at each street intersection and at intermediate points between intersections. Hydrant interval shall not be greater than 700 feet. Hydrants shall be located so that no structure is situated more than 500 feet from a hydrant as measured along the street and driveway. The hydrant lead shall be a minimum of 6 inches in diameter. Auxiliary valves shall be installed in all hydrant leads 4 feet from the hydrant. New hydrants shall be placed a minimum of 6 feet but not more than 10’ from the edge if the road surface. These dimensions may be adjusted with prior approval of the Water Department.
H. Where dead-end mains occur they shall be provided with a fire hydrant if flow and pressure are sufficient, or with an approved flushing device. No flushing device shall be directly connected to any sewer. No water service shall be connected beyond the end hydrant.
I. Air Relief Valves. At high points in the water mains where air can accumulate, provision shall be made to remove the air by means of hydrants or air relief valves. Automatic air relief valves shall not be used in situations where flooding of the manhole or chamber may occur.
J. Surface Water Crossing. Surface water crossings, whether over or under water, present special problems.
1. Above Water Crossing: The pipe shall be adequately supported and anchored, protected from damage and freezing, and accessible for repair or replacement.
2. Underwater Crossing. A minimum earth cover of 4 feet shall be provided over the pipe. When crossing watercourses that are greater than 15 feet in width, the following shall be provided. The pipe shall be of special construction, ductile, cement lined, with flexible watertight joints. Pipe shall have restraints at all underwater connections. Valves shall be provided at both ends of the water crossing to allow that section of main to be isolated for testing or repair. The valves shall be easily accessible, and not subject to flooding. Sample/pressure test taps shall be installed near the main valves for testing of the underwater crossing.
3. HDPE (water main grade plastic pipe) may be directionally bored under a body of water. Installation of valves shall be the same specifications as applied to ductile iron pipe.
K. Cover. All water mains shall have a minimum of 5 feet of cover as measured from the top of the pipe.
L. Easements. Water main easements shall have a minimum permanent width of 20 feet. There shall also be work easements of an additional 20-foot width.
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