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Study on IAPMO’s Water Demand Calculator Reveals Energy, Carbon, and Water Savings


A new study reveals the benefits of using the International Association of Plumbing and Mechanical Officials’ (IAPMO) Water Demand Calculator, showing that using the tool as an alternative to sizing methods in traditional plumbing codes can result in energy, carbon, and water savings.

IAPMO developed the Water Demand Calculator in response to the consistent oversizing of potable water distribution systems in the built environment. The calculator predicts peak water demand for single and multifamily dwellings and removes the need for assigning fixture units to plumbing fixtures and corresponding to Hunter’s probability curve (which was developed over 80 years ago). Instead, it directly calculates peak demand using algorithms based on a building’s size.

Research included a single-family home, and six-unit, 45-unit, and high-rise multifamily residences.

IAPMO commissioned Arup to analyze and better understand the tool’s potential for sustainability savings. Ultimately, using the calculator resulted in operational carbon savings between 73% and 84% in the high-rise apartment example. Additionally, water savings were achieved “through minimized time to tap using the Water Demand Calculator sizing and range from 450 gallons to 71,000 gallons annually, depending on the building size,” IAPMO reported.

“The Water Demand Calculator is a tool for its age,” said IAPMO vice president of technical services and research Christoph Lohr. “With concerns of energy reduction and water savings being top of mind for many regions in the United States and the world, having the latest methodology to meet goals is vital. We greatly appreciate Arup providing IAPMO with a third-party evaluation of the potential for the Water Demand Calculator to help meet sustainability goals.”

Access the Arup report and download the Water Demand Calculator.

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