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DISTRIBUTION SYSTEM PIPING AND APPURTENANCES PART 8 <br /> 8.2 SYSTEM DESIGN <br /> 8.2.1 Pressure <br /> All water mains, including those not designed to provide fire protection, shall be sized after a <br /> hydraulic analysis based on flow demands and pressure requirements. The system shall be <br /> designed to maintain a minimum pressure of 20 psi (140 kPa)at ground level at all points in the <br /> distribution system under all conditions of flow. The normal working pressure in the distribution <br /> system shall be at least 35 psi (240 kPa)and should be approximately 60 to 80 psi (410 -550 kPa) <br /> and not less than 35 psi (240 kPa). <br /> 8.2.2 Diameter <br /> The minimum size of water main which provides for fire protection and serving fire hydrants shall <br /> be six-inch diameter. Larger size mains will be required if necessary to allow the withdrawal of the <br /> required fire flow while maintaining the minimum residual pressure specified in Section 8.2.1. <br /> The minimum size of water main in the distribution system where fire protection is not to be <br /> provided should be a minimum of three(3)inch diameter. Any departure from minimum <br /> requirements shall be justified by hydraulic analysis and future water use, and can be considered <br /> only in special circumstances. <br /> 8.2.3 Fire protection <br /> When fire protection is to be provided, system design should be such that fire flows and facilities <br /> are in accordance with the requirements of the State Insurance Services Office. <br /> 8.2.4 Dead ends <br /> a. be rrdnkrdzed by meting mprivirde Wins**mew 'holder <br /> provide inceeeed reWailify of service and reduce heed toes. <br /> b Dead end mains shall be equipped with a means to provide adequate flushing. Flushing <br /> devices should be sized to provide flows which will give a velocity of at least 2.5 feet per <br /> second in the water main being flushed. They may be provided with a fire hydrant if flow and <br /> pressure are sufficient. No flushing device shall be directly connected to any sewer. <br /> 8.3 VALVES <br /> A sufficient number of valves shall be provided on water mains to minimize inconvenience and sanitary <br /> hazards during repairs. Valves should be located at not more than 500 foot intervals in commercial <br /> districts and at not more than one block or 800 foot intervals in other districts.Where systems serve <br /> widely scattered customers and where future development is not expected,the valve spacing should <br /> not exceed one mile. <br /> 8.4 HYDRANTS <br /> 8.4.1 Location and spacing <br /> a. Fire hydrants should be provided at each street intersection and at intermediate points <br /> between intersections as recommended by the State Insurance Services Office. Generally, <br /> fire hydrant spacing ranges from 350 to 600 feet depending on the area being served. <br /> -116- <br /> 116 <br />