Comparing Actual and Designed Water Demand in Australian Multilevel Residential Buildings

Abstract

There is now evidence that many long-standing international plumbing codes significantly overestimate the peak water demand in multilevel residential buildings. The overestimation of this design value may have adverse effects on construction cost, energy con- sumption, water quality, and safe operation. This research aims to assess the performance of the current Australian and New Zealand cold water plumbing standard in peak demand design for multilevel residential buildings. A literature review was conducted on the international development of residential water demand estimation models. The Australian practice of peak demand design is compared against selected international plumbing codes and some newly proposed approaches using a fixed apartment layout as a benchmark. Following this, the paper compares the actual water demand of four Australian multilevel residential buildings with the designed peak demand (99th percentile flow) from the Australian and New Zealand standard and selected international plumbing codes. Results show that the adjusted 99th percentile flow rates (adjusted from raw measurements to count for the impact of sampling interval) are only 23%–28% of the nominal design values from the Australian and New Zealand standard. None of the international peak demand design standards considered in this research can be readily applied to Australian multilevel residential buildings. Research needs are identified, including the impact of the sampling interval, the practical definition of the 99th percentile flow, the implications of reduced pipe sizes, and other limitations in current plumbing system design practices. This research serves as an informative reference for researchers, industry, and regulatory bodies work- ing on improving their existing plumbing design standards