A revolutionary tool, the Water Demand Calculator® more accurately estimates peak water demand in single-family homes and apartment buildings, reducing the carbon footprint of the structure and saving consumers on both their water and water heating-related energy utility bills for the entire life of the plumbing system. At the same time, proper sizing greatly minimizes the potential threat of bacterial growth within the system, which can lead to such serious health risks as Legionnaire’s disease.

In 2021, the Statewide Utility Codes and Standards Team submitted a Title 24 Petition to adopt Appendix M into the CPC during the 2022 Intervening Code Adoption Cycle. The petition was accompanied by the letters of support from 20 organizations including the California Legislature, cities, water utilities, engineering firms, and the California Water Efficiency Partnership.

The Water Demand Calculator is the first major update impacting plumbing sizing since the 1940s. It is the result of a multiyear effort to develop a new statistically based pipe sizing method stemming from a need to address profound water safety and wasted water and energy concerns resulting from oversized water supply pipes in homes and buildings.

California joins states including Nevada, North Dakota, Oregon and Wisconsin, as well as the cities of Seattle, Washington and Vancouver, British Columbia, in adopting Appendix M into their codes and standards.