Head Losses at Sewer Junction Manholes

Head losses at sewer pipe junctions have been studied in a model. The junction geometry was varied by using manholes of different widths and cross-sections, and by using various arrangements inside the manholes. The pipe diameter and alinement upstream and downstream of the junction were identical. In all experiments, pipes were flowing under pressure, but a free water surface was maintained inside the junction manhole. Observed piezometric heads and flow velocities served to calculate the upstream and downstream energy grade lines and the junction head loss. The head loss was found to increase linearly with the increasing velocity head and the observed experimental relationship was therefore approximated by a regression line. The head loss coefficient was then determined as the slope of the regression line. Head loss coefficients are presented for nine cases studied.