Simulation of building drainage system operation under water conservation design criteria

The Water Supply (Water Fittings) Regulations 1999, introduced to encourage innovation and water conservation, will profoundly affect building drainage design. Reduced shower flows and washing machine volumes and 6/3 litre dual flush WC operation will lower throughflows, while drop valve WC flushing will affect system operation. Design for water conservation will necessitate the prediction of wave attenuation and its impact on solids transport and, without the safety factor provided by higher throughflows, simulations will ensure efficient design for minimal solid deposition. A simulation employing the method of characteristics solution of the St Venant equations and empirical relationships between solids velocity and the surrounding flow conditions is presented to predict solids transport performance within networks specified by slope, diameter, material, and appliance distribution and discharge characteristics.