IAPMO Offers Residential Water Demand Calculator

The calculator, embedded in a familiar Microsoft Excel file (2009 or later), typically results in a 15 to 65 percent reduction in water use estimates for a home.

According to Contractor Mag, “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 2018 UPC and the 2017 WE•Stand are published as American National Standards.”

They add that:

“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. To assist plumbing system designers and to encourage proper use and promote uniform application of the new approaches for estimating peak indoor demands, the WDC has been developed in a Microsoft Excel spreadsheet that can be downloaded at http://www.iapmo.org/WEStand/Pages/WaterDemandCalculator.aspx.