The International Association of Plumbing and Mechanical Officials (IAPMO) have made available a Water Demand Calculator (WDC) that estimates peak water demand in residential buildings. The WDC will appear in the appendices of both the 2018 Uniform Plumbing Code (UPC) and the 2017 Water Efficiency and Sanitation Standard (WE•Stand).

The WDC provides an easy-to-use, statistically based method for estimating peak water supply demand for single and multifamily residential dwellings, resulting in more accurately sized systems consistent with the lower flow rates and consumption values from water-efficient plumbing fixtures and appliances.

IAPMO initiated a Memorandum of Understanding with the American Society of Plumbing Engineers (ASPE) and the Water Quality Research Foundation (WQRF) to form a special task force to revise the methodology for properly estimating premise plumbing water supply demands in response to the increased use of water-conserving plumbing fixtures, fixture fittings and appliances, and the subsequent decreased demand for water in single and multifamily residences.

“I am very pleased with the outcome of this six-year study and to present the first new method for estimating peak demand since Dr. Hunter’s innovative curve from 1940 to the plumbing engineering community,” said Dan Cole, senior director of technical services for IAPMO and Secretariat for WE•Stand. “With the use of the new WDC, we are finally bringing Hunter into the 21st century. For now, the WDC is applicable for only residential dwellings from single to multifamily apartment dwellings. However, our work is far from done. Along with ASPE and WQRF, we are already in the planning phases for a nonresidential-use WDC and possibly an associated app so that the plumbing design community can easily access and use this new important tool.”

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