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Studies Detail the Cost Saving Potential of the Water Demand Calculator

There is a tremendous need for practical, water-related demand-side water research that helps communities safely implement policies related to water and energy efficiency and meet the growing list of challenges threatening drinking water quality in the United States. Profound concerns about water safety and wasted water and energy resulting from oversized water supply pipes in home and buildings, motivated IAPMO to lead a research project along with the American Society of Plumbing Engineers (ASPE), the Water Quality Research Foundation (WQRF), and the University of Cincinnati, to develop a new statistically based pipe sizing method.

This multi-year effort resulted in the development of the Water Demand Calculator (WDC) – the most important innovation in pipe sizing in almost a century.1

Along with addressing the primary concerns of water safety and efficiency, applying the WDC also provides significant cost reductions resulting from the use of smaller water pipes, fittings and related components and from lower utility connection and water use fees. This paper discusses the potential economic benefits of applying the WDC over traditional pipe sizing methods in the construction of residential buildings2.

Two studies were conducted as part of this project.

  • IAPMO commissioned Stantec Architecture to calculate the material and labor costs saving potential of applying the WDC as compared to applying the sizing methods contained in baseline plumbing codes, specifically, IAPMO’s Uniform Plumbing Code, the International Code Council’s (ICC) International Residential Code (IRC) and the ICC’s International Plumbing Code (IPC).
  • IAPMO also commissioned the Alliance for Water Efficiency (AWE) to conduct a study investigating the cost savings resulting from reduced meter connection fees and utility water use fees, which are based on water meter size. Both studies are available for download HERE.

The results from the two studies show significant cost savings potential associated with applying the WDC. For example, the total average savings for a typical 2,379 square foot single family home in a high cost labor market can exceed $2,000.00 and can be as high as $5,000.00, depending on location. For multi-family apartment buildings, the potential savings are even higher and can exceed $100,000.00 on a 45-unit multi-family building, especially where utility meter connection fees are high due to water scarcity.

1 Visit https://www.iapmo.org/water-demand-calculator/ to learn the technical details about how the WDC works and how to download it.

2 The WDC is currently only applicable for residential buildings. However, currently planned research pertaining to water use patterns in non-residential building will allow for the future use of the WDC in non-residential buildings.

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Adaptive Reuse: Converting Offices to Multi­Residential Family

Adaptive reuse of commercial office spaces to residential multifamily offers opportunities to ease some of the housing shortage in the US. These types of construction projects have many challenges, from zoning restrictions, financing, and also controlling construction costs. Construction costs specifically can have a disparate impact on whether an adaptive reuse project is possible, let alone successful. Therefore, flexibility during the construction process is vital to the success of an adaptive reuse project. Codes for plumbing and mechanical systems that support design versatility and science-based methods, such as the Uniform Codes, will be essential for controlling construction expenses.

Capacities of Stacks and Horizontal Drains in Storm Drainage Systems

The sizing for storm drainage systems are dependent upon flow capacity equations used to calculate velocities and flow rates in pipe conduits. One of the variables in the equations is the coefficient of roughness. This paper explores how the roughness of different types of material will change the computational results that are dependent upon the roughness coefficient of the pipe.

Increase in Flow Diversity From Simultaneous Fixture Use: Impact on Peak Flow Estimate

In calculating peak water demand, there can be instances where an increase in fixture count results in a decrease in the expected peak demand. This white paper explains why this counterintuitive result can occur, especially when there is some probability of stagnation (i.e., zero demand). Using IAPMO’s Water Demand Calculator (WDC), we are not designing with zero flow in mind; hence, zero flows are ignored, and the 99th percentile is extracted from actual flows for any combination of busy fixtures.


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