Experimental study on the hydraulic performance of the horizontal main drain of building drainage systems with solid waste

Water–air two-phase flow has been the theoretical basis of traditional building drainage systems. However, with the popularization of water-saving devices, more research investigations need to be performed on the impact of solid waste on drainage systems. Through experiments under the solid waste scenario, the effects of drainage volume, diameter, and slope of the pipeline on the hydraulic performances of the horizontal main drain were investigated. The results showed that the depth ratio was mainly responsible for the change of positive pressure value in the horizontal main drain. The depth ratios and the positive pressure values were proportional to the drainage volumes and inversely proportional to the diameters and slopes of the pipeline. The final deposition distances of solid wastes in the horizontal main drain were proportional to the discharge volumes and the pipeline slopes. However, the effects of pipe diameters and flow rates on final deposition distances need to be considered in sections. The self-cleaning lengths based on clear water were 1.2–1.6 times the real final deposition distances of solid wastes.