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Planning engineers commonly use generous factors of safety for peak flow estimates in urban water supply systems both as a hedge against unforeseen growth and because economies of scale result in relatively low user costs even with such reserve capacity. Transplanting of such design criteria into the rural setting, however, simply does not work. The low density portions of rural domestic systems require very realistic design criteria or the construction costs become infeasible for the small number of customers involved. Peak instantaneous flow rates in a Utah rural system were measured continuously during two summers on three dead-end lines serving various numbers of customers. The second summer included measurement of flows to customers whose maximum flow rate was limited by a simple orifice placed in each meter. Conclusions which emerged from this study included: 1) Actual peak demands were lower than those required for design purposes by some state regulatory agencies, but higher than the Farmers Home Administration minimum standard. 2) Where extremely small mains are required by the economics of low density situations, or where unforeseen growth is overtaxing system capacity, peak demands can be cut significantly by simple, flow restricting devices at each meter without decreasing the quality of water service to the customer. 3) Field measurements of head loss through 10 year old plastic pipe indicated a Hazen Williams friction factor average of 133.


Publication made available electronically April 26, 2012.