B034 Domestic flush demand

Monte-Carlo solution of domestic flushing water consumption in Hong Kong

Brief:

Toilet flushing has been identified as one of the key issues in sustainable water system designs for buildings as it could be the single activity contributing to the highest water consumption in domestic applications. Indeed, flushing water consumption is of primary importance in designing a plumbing and drainage system for buildings. Flushing water demands are transient and influenced by occupant load variations, occupant usage patterns, installed appliances, and system commissioning. Apart from the system installed, however, there is a lack of concern about the consumption due to occupant usage patterns in building estates having a high population density. This paper proposes a Monte Carlo solution of daily domestic flushing water consumption for residential developments. The model parameters, including the installed cistern capacity of water closets, variations of occupants’ demands, occupant load and its diurnal variations, were determined from recent studies on domestic WC usage patterns of residential buildings in Hong Kong. In particular, numerical values of the parameters were sampled from density functions using the Monte Carlo technique in order to determine the probable flushing water consumption for a residential development. Predictions were made for typical residential buildings in Hong Kong and verified with on-site measurements. The modeled results showed that occupant load and its variations had significant influence on domestic flushing water consumption. The model, with appropriate parameters selected, would be a useful source of reference to planning for domestic flushing water consumption in residential developments.

Further information:

Wong LT, Mui KW, 20006. Monte-Carlo solution of domestic flushing water consumption in Hong Kong, Sichuan-Hong Kong Joint Symposium 2006 – Trends and Challenges in Green, Healthy and Safe Buildings, HKIE/ASHRAE/CIBSE, 30 Jun-1 Jul, Chengdu, China, pp. 8-14.