Water and Wastewater Terms Beginning H
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head loss
The head, pressure, or energy (they are the same) lost by water flowing in a pipe or channel as a result of turbulence caused by the velocity of the flowing water and the roughness of the pipe, channel walls, or fittings. Water flowing in a pipe loses head as a result of friction losses. In a filter, friction losses are caused by material buildup. Also see friction loss.