IAPMO has launched WDC-Pro, a web-based tool designed to improve the efficiency and accuracy of water pipe sizing for multi-family, high-rise, and residential buildings.

Building on the success of the original IAPMO Water Demand Calculator, which has been adopted in 10 states and multiple cities, WDC-Pro streamlines complex calculations, particularly for multi-family applications, reducing design time by 50% or more while optimizing pipe sizing to reduce construction costs and enhance water efficiency. This reduces calculation time from six hours to just two or three for large-scale projects.

The primary benefit of WDC-Pro is that it uses templates to compute the instantaneous water demand expected during the period of peak indoor water use in multi-family buildings such as apartments and condominium complexes. The user provides the number and flow rate for each type of indoor fixture in the residential building. WDC-Pro summarizes the input data and returns an estimate of the corresponding 99th percentile of the instantaneous water demand.

“While the base Excel version of the Water Demand Calculator will remain free to download, there was a need for an enhanced tool to streamline water calculations, especially for design professionals of multi-family buildings,” said IAPMO Vice President of Technical Services and Research Christoph Lohr, PE. “This need has resulted in the creation of a subscription-based WDC-Pro, a tool that aims to fit into the normal design process for most design professionals.

“Additionally, this tool aims to simplify the process to report calculations to the authority having jurisdiction (AHJ). We are excited for this initial version to be released and look forward to continuing to improve the functionality of this tool to better support and align with the plumbing design professional, plumbing installer, and plumbing AHJ needs.” 

The traditional method for sizing plumbing pipes, developed in the 1940s, assumes simultaneous use of all fixtures — an outdated approach that leads to oversized pipes, increased costs, and unnecessary water waste. The Water Demand Calculator methodology, now expanded with WDC-Pro, uses modern water usage data to determine the right pipe sizes, reducing material costs and water stagnation risks linked to biofilm growth and Legionella bacteria.

Key benefits of using the Water Demand Calculator in multi-family calculations include the following:

• Cost Reduction – A 276-unit building saved $134,000 by optimizing pipe sizing.
• Water Efficiency – Reduces water waste between 250-500 gallons per dwelling unit by delivering hot water more quickly. This is the equivalent of an outdoor hot tub of water savings every year.

WDC-Pro is available now through a monthly or annual subscription at https://wdcpro.iapmo.org/.