Drainage flow and solid transport simulation in defective building drainage networks

The flow conditions within multi-storey building drainage networks may be characterized as unsteady free surface flows and as such may be analyzed and simulated by the use of the method of characteristics to solve numerically the governing equations of continuity and momentum. However the application of such simulations must take into account the possibility of defective system installation and must be able to predict the wave attenuation following appliance discharge and the consequent effects upon solid transport due to system defects caused by faulty installation or the development of obstructions to the flow. This paper presents both a summary of a detailed survey of defects in installed building drainage networks and the development of appropriate boundary conditions that allow the method of characteristics based computer simulation to accurately predict the effect of defects on system performance. The introduction of drainage simulations capable of providing design advice under the real conditions represented by this study is particularly timely in view of governmental pressure for water conservation and the introduction in 1998 of the new Water Regulations to replace the Water Bye-Laws that will introduce reduced and dual flush w.c. operation, together with reduced shower and other appliance flows.