Reduction in water pressure between a pump or hydrant and a nozzle due to expenditure of pressure energy required to move water through a hose; includes losses due to back pressure, friction loss, elevation loss, and/or losses in fittings.
The term given for the loss of pressure that occurs whenever water moves through a pipe or when water moves uphill against the force of gravity. If the total pressure loss in a piping system exceeds the available static water pressure the water will not flow.
When liquid flows through a certain segment, the energy of the liquid is lost due to friction against the internal wall of the pipe, changes in pipe shape, diversion of flow, merge of flow, and internal obstacles, etc. The pressure loss is represented as the difference of total pressure at the beginning and end of the segment.