Castle Rock, Colorado — The Castle Rock, Colorado, town council has approved the adoption of IAPMO’s Uniform Plumbing Code (UPC®) Appendix M — the Water Demand Calculator® — as an alternative methodology for sizing water pipes in single- and multifamily buildings. The Castle Rock Town Code has been amended to require the use of the Water Demand Calculator for sizing water service lines and internal plumbing supply lines.
A revolutionary tool, the Water Demand Calculator accurately predicts 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 Legionnaires’ disease.
Castle Rock, a community of 85,000 located 30 miles south of Denver, has set a goal of utilizing 100 percent renewable water sources by 2065 and hopes to achieve 75 percent by 2050. The Water Demand Calculator will contribute to that effort by reducing the amount of water unintentionally wasted by residents. The use of the Water Demand Calculator will reduce the minimum required pipe sizes within each residence, reducing the potential water age of the water within the plumbing system. This will minimize the risk of water quality issues and also have a positive effect on water conservation by allowing hot water to get to fixtures more quickly.
“This change to Town Code will support our water conservation efforts by right sizing the water supply side plumbing, while also helping to protect water quality, supporting requirements for additional water conserving plumbing fixtures and reducing material costs for home construction,” said Matthew Hayes, P.E., Castle Rock Technical Engineering manager.
Castle Rock is the first town in Colorado to adopt Appendix M into its codes and standards, joining such major cities as Seattle, San Jose, and Vancouver, British Columbia, as well as the states of California, Hawaii, Montana, Nevada, New Jersey, New Mexico, North Dakota, Oregon, Washington, and Wisconsin.
“IAPMO appreciates the vision of the Castle Rock town council and thanks Director of Castle Rock Water Mark Marlowe, Water Efficiency Supervisor Rick Schultz, and Technical Engineering Manager Matthew Hayes for their advocacy as IAPMO and Castle Rock worked together to realize this adoption,” said IAPMO Vice President of Technical Services and Research Christoph Lohr, P.E.
The Water Demand Calculator represents the most impactful innovation in pipe sizing in nearly a century. 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.
The Water Demand Calculator version 2.2 and user guide, as well as related videos, are available at https://www.iapmo.org/we-stand/water-demand-calculator/water-demand-calculator-california. For specific information about the Water Demand Calculator or to provide feedback, please contact Lohr at christoph.lohr@iapmo.org.
IAPMO®, developer of the Uniform Plumbing Code (UPC®) and Uniform Mechanical Code (UMC®), has posted online the timeline for the development of the 2030 editions of these prospective American National Standards.
IAPMO® is seeking volunteers to participate on two technical committees working toward the development of the 2030 editions of the Uniform Plumbing Code (UPC®) and Uniform Mechanical Code (UMC®). The deadline to submit an application is Jan. 30, 2026.
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