Stochastic modelling of water demand by domestic washrooms in residential tower blocks

Accurate estimates of probable simultaneous maximum demand are essential for appropriate decisions on sizing water supply plants and piping systems for high-rise residential buildings at a balance of acceptable plant reliability and construction cost. This study proposes a stochastic model of the probable maximum simultaneous water demands of domestic washrooms at some usage patterns for which the appliances in the same washroom would not operate simultaneously. The model parameters were determined from surveys of usage patterns in 597 domestic washrooms of typical high-rise residential buildings in Hong Kong. The results showed that the probable maximum simultaneous demands due to a number of domestic washrooms in a typical high-rise residential building were only about 50-60% of those estimates with an assumption of all appliances in simultaneous operation. This study is a useful source of reference in determining loadings of water supply plants and piping systems for high-rise residential buildings.