Oklahoma City, Oklahoma — The Oklahoma Uniform Building Code Commission (OUBCC) has unanimously approved the adoption of IAPMO’s Uniform Plumbing Code (UPC®) Appendix M — the Water Demand Calculator® — into Chapter 6 of the state’s adopted International Plumbing Code as an alternative methodology for sizing water supply piping in single- and multifamily buildings.
The alternative approach will be available for voluntary statewide use beginning Sept. 14.
A revolutionary tool, the Water Demand Calculator accurately predicts peak water demand in single-family homes and apartment buildings, reducing a building’s carbon footprint while lowering water and water heating-related energy costs throughout the life of the plumbing system. Proper pipe sizing also minimizes water stagnation, reducing the potential for bacterial growth that can contribute to serious public health risks such as Legionnaires’ disease.
The OUBCC establishes minimum statewide building standards. Local jurisdictions retain the authority to adopt more stringent requirements but may not adopt standards less stringent than those recognized by the commission.
“IAPMO appreciates the Oklahoma Uniform Building Code Commission for recognizing the value of modern pipe-sizing methods that improve both public health and water efficiency,” said Christina Kaeini, IAPMO senior director of Government Relations, who testified before the commission in support of the proposal. “The Water Demand Calculator gives designers another science-based option that reflects today’s plumbing fixtures and water use patterns while helping reduce construction costs, conserve water and energy, and improve water quality within premise plumbing systems. We’re grateful to the commission, stakeholders, and our industry partners for their thoughtful consideration and support.”
The Water Demand Calculator addresses water quality concerns associated with oversized premise plumbing systems while simultaneously reducing water and energy use and lowering construction costs. Representing the most significant advancement in residential water pipe sizing in nearly a century, it is the result of a multiyear research effort to develop a statistically based methodology that reflects modern plumbing fixtures and actual water demand, replacing assumptions developed decades ago.
Oklahoma becomes the 11th state to adopt Appendix M into its codes and standards, joining California, Hawaii, Montana, Nevada, New Jersey, New Mexico, North Dakota, Oregon, Washington, and Wisconsin, as well as major cities including Houston, San Jose, Seattle, and Vancouver, British Columbia.
Learn more about the Water Demand Calculator at iapmo.org/we-stand/water-demand-calculator.
IAPMO® is pleased to announce the publication of IAPMO/ANSI/CAN Z1403-2026, Water Demand Calculator®, a new American National Standard and National Standard of Canada that provides a modern, statistically based method for estimating peak water demand in single-family and multifamily residential buildings.
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