Determination of Fixture-Use Probability for Peak Water Demand Design Using High-Level Water End-Use Statistics and Stochastic Simulation

Some recent studies have used actual water end-use data to inform the peak demand design of plumbing systems in residential buildings, addressing the problem of overestimation in many long-standing plumbing codes and standards. Vast amounts of fixture-specific data from each household are required to determine the frequency each fixture is used during peak water consumption periods (fixture-use probability). However, obtaining such data can be difficult, and the processing is costly and time-consuming. The current study presents a new approach for determining the fixture-use probability for peak water demand design of premise plumbing systems. A stochastic water demand model is developed using only the high-level statistical information from water end-use studies presented in the public domain, offsetting the need for the original water end-use data sets. The stochastic model is then used to form easy-to-use formulas for determining the probability of use for various fixture groups, which consider both the number of apartments and building occupancy. The approach is validated by comparing the estimated peak demand values with the corresponding values determined from actual water consumption observations in three Australian residential apartment buildings and one mixed-use building. The new approach enables a much more accurate estimation of the peak demand compared with the conventional approach suggested in the current Australian plumbing standard. The proposed approach can be used by researchers and practitioners in other countries to determine their region-specific fixture-use probability values for more accurate peak demand estimation, contributing to improved premise plumbing system design.