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<br />much of the calculations. A map showing the water pipelines within the Town including <br />numbered identification of pipes and nodes is included in Appendix A. Water supply and <br />withdrawal points are located at nodes. <br /> <br />B. Water Demand For Analysis Purposes <br /> <br />As previously described, water usage is allocated throughout the distribution system based on <br />location and number of water taps within certain areas often encompassing approximately one <br />town block. For purposes of water system analysis, peak hourly usage has been simulated to <br />provide a worst case condition. Peak water usage per tap has been derived as folloWs by dividing <br />estimated peak hourly demand by the number of taps served: <br /> <br />P ak t d d ta - 1700g.p.m. - 1 96 It <br />e wa er eman per p - 865 taps -. g.p.m. ap <br /> <br />To simplify calculations slightly, peak water demand per tap in the computer program as been <br />assumed to be 2 g.p.m./tap. <br /> <br />Accurate determination of required water supply for fire flows is beyond the scope of this study, <br />however a review ofInsurance Services Office (ISO) guidelines and information obtained from <br />local fire department personnel have indicated minimum desired flows at a fire hydrant is 500 <br />g.p.m. with a residual water pressure of 20 p.s.i. However, the needed fire flow for 1 and 2 <br />family dwellings not exceeding 2 stories in height with 31-100 feet between buildings is 750 <br />g.p.m. per ISO 1980 guidelines. For purposes of this study, the higher 750 g.p.m. fire flow has <br />been used to be conservative. The water supply system should be able to meet peak daily usage <br />plus the minimum fire flow for at least two hours. Following are calculations comparing <br />available water supply and storage to fire flow requirements: <br /> <br />Assume peak daily usage = 1,450 g.p.m. <br />Required fire flow = 750 g.p.m. <br />Total required flow rate = 2,200 g.p.m. <br /> <br />V olume of water required for fire flow: <br /> <br />2,200 g.p.m. x 2 hrs. x 60 min./hr. = 264,000 gallons <br /> <br />Existing storage plus pumping capacity: <br /> <br />Lower tank <br />Upper tank <br />1,450 g.p.m. x 2 hrs. x 60 min./hr. <br />Total 2 hr. Supply <br /> <br />= 272,000 gallons <br />= 215,000 gallons <br />= 174,000 gallons <br />661,000 gallons <br /> <br />9 <br />