In 2012, the International Association of Plumbing and Mechanical Officials (IAPMO), the University of Cincinnati (U of C), and the American Society of Plumbing Engineers (ASPE) began to work on a new sizing technique 80 years in the making. The main drivers were Dan Cole (IAPMO) and Steve Buchberger (U of C), and later Toju Omaghomi (U of C). As part of this effort, hundreds of thousands of data points were taken and evaluated to determine actual human behavior and plumbing fixture use in residential homes.
The data was evaluated and a new calculation tool was developed. This method was ultimately dubbed “The Water Demand Calculator” (WDC), and the WDC was ultimately added to the 2018 UPC as “Appendix M.” This marked the first time in almost 80 years that an alternative to Hunter’s Curve pipe sizing methodology was added to a model code.