Correction of Head Loss Measurements in Water Mains

Pipe roughness or carrying capacity are occasionally determined in water mains to assess the internal condition of the mains or determine coefficients for pipe network models. As part of these tests, it it necessary to measure the head loss between two points in the pipe. Two methods are commonly used to determine the head loss: (1) two gage method; and (2) parallel pipe method. The effect of the differing temperatures in the main and parallel pipe is theoreticlly determined and a means for compensating for this effect is suggested. The parallel pipe method can be an extremely accurate method for measuring head loss in water mains. When the tests are conducted in hilly areas, caution must be exercised since the gage reading may not exactly correspond to the head loss, in which case a correction would be necessary to account for the effect of water temperature difference between the main and the parallel pipe.