Measurements of the hydraulic roughness of slimed sewers and pipes

A series of experiments on the effect of sliming on the hydraulic roughness of foul sewers has been carried out on a specially-constructed rig at a sewage pumping station at Littlemore, Oxford. Three separate runs of 335,206 and 188 days duration were conducted on a continuous pipeline made up of vertically-cast concrete, uPVC, spun concrete, asbestos-cement and unglazed pipes at a gradient of 1 in 250 and a velocity of 1.2m/s. In each test the flow was varied continuously on a daily circle with a peak at 1000 hours, giving approximately helf-full depths, and a secondary minor peak at 1900 hours.