Hunter’s Curve has been the tried-and-true formula for engineers to estimate peak water demand in buildings since the 1940s. The formula takes into account variables such as the number of fixtures, the flow rate, number of people in the building, and the duration of use of the fixtures. But because some of these variables can change drastically over time, experts are taking a shot at updating the formula for modern plumbing fixtures.

“Today’s engineers and contractors have a variety of factors to consider, such as green technology, touch-free fixtures, hygiene concerns and more, bringing about a need for a calculation that more accurately predicts peak water demand,” Kay Herbert, Ph.D., chief scientist at Sloan, writes in an article for PCHPPros. “That’s why I developed a new formula yielding more accurate water demand estimates to meet the challenges of today’s buildings. While my formula can be applied to residential buildings as well, commercial facilities with varying water pressures, high-efficiency fixtures and many different fixture types will benefit from it the most.”

Herbert lays out his formula in the article, comparing it to Hunter’s Curve and explaining in detail why he sees his approach as a much-needed update for next-generation plumbing, with a focus on improving plumbing cost, hygiene, and sustainability factors. For projects at an earlier planning stage, our tankless sizing infographic provides a quick snapshot that helps you estimate the size of the tankless water heater array that projects of various sizes will require.

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