Effect of pipe size and location on water-main head loss in water distribution systems

This study discusses practical implications of considering unit head loss in different pipe sizes and in different locations of water distribution systems (WDSs) with regard to operation and maintenance. By visualizing unit head loss (using the Hazen-Williams relationship) in pipes obtained from 18 WDSs in North America, changes in unit head loss are put into perspective in different pipe sizes and different WDS locations. The results suggest that the importance of diameter is greater than that of the Hazen-Williams roughness factor, that flow rate plays a more important role than diameter in determination of head loss in pipes closer to water sources, and that diameter seems to be more important than flow rate in pipes at the periphery. Moreover, aging, tuberculation, and subsequently reduction in effective diameter can have a more critical effect on head loss in smaller pipes at the periphery of a system. Finally, effects of water conservation and pump scheduling in different locations of the network, as far as head loss is concerned, can potentially be more evident on larger pipes closer to the water source and in some cases on smaller pipes at the periphery. Therefore, it is suggested that network-level energy management decisions can have different effects on different pipe sizes in different locations.