DENVER, CO — Colorado has approved a science-based method for sizing water supply piping, giving designers and builders a voluntary alternative intended to improve plumbing system performance, water efficiency and public health.

The Colorado Plumbing Board unanimously approved IAPMO’s Uniform Plumbing Code® (UPC®) Appendix M—the Water Demand Calculator®—for inclusion in Chapter 6 of the state’s adopted International Plumbing Code. The methodology can now be used statewide for sizing water supply piping in single- and multifamily buildings.

Water Demand Calculator Updates Traditional Pipe Sizing

Traditional water supply pipe-sizing methods rely heavily on assumptions developed decades ago, when plumbing fixtures and household water-use patterns were different from those common today.

The Water Demand Calculator uses statistical analysis to predict peak water demand based on modern plumbing fixtures and actual patterns of water use. By matching pipe capacity more closely with expected demand, the methodology can help address the oversized piping that can result from conventional approaches.

“IAPMO commends the Colorado Plumbing Board for adopting a modern, science-based approach to pipe sizing,” said Christina Kaeini, IAPMO Senior Director of Government Relations. “The Water Demand Calculator reflects today’s water use patterns and can help lower costs, improve efficiency, and enhance water quality. We appreciate the board’s leadership and the support of stakeholders and industry partners.”

Right-Sizing Can Reduce Water and Energy Use

Properly sized water supply piping can reduce construction costs while limiting the amount of water and water-heating energy required to operate a plumbing system.

Right-sizing can also improve hot-water delivery by reducing the volume of water contained within premise plumbing systems. Reducing unnecessary water volume can limit stagnation and help reduce conditions that may contribute to bacterial growth, including Legionella.

The Water Demand Calculator is the result of a multiyear research effort to develop a statistically based approach to water supply pipe sizing. Its methodology is intended to better align pipe capacity with actual demand while supporting more efficient use of water and energy.

Colorado Joins Growing List of Adopters

The Colorado Plumbing Board establishes minimum statewide building standards. Local jurisdictions may adopt more stringent requirements but may not adopt standards less stringent than those recognized by the board.

Colorado is the 12th state to adopt Appendix M into its codes and standards. Other states include California, Hawaii, Montana, Nevada, New Jersey, New Mexico, North Dakota, Oklahoma, Oregon, Washington and Wisconsin.

The Water Demand Calculator has also been adopted by 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.