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The IAPMO expects the calculator to provide a reduction in water demand estimates
The International Association of Plumbing and Mechanical Officials (IAPMO) has developed a Water Demand Calculator (WDC) that estimates peak water demand in residential buildings. The WDC provides a 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 (MOU) 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 family residences.
The WDC eliminates the need to count fixture units and replaces an outdated design curve that does not take modern water flows into account. To facilitate easy usage, the WDC requires the input of the number of plumbing fixtures for the building supply or the individual branches and risers and directly computes the peak. Use of the WDC is estimated by the IAPMO to provide between a 15 to 65% reduction in water demand estimates, depending of the size of the residential structure, when compared to current pipe sizing methods.