IAPMO Water Demand Calculator

Build smarter with right-sized pipes

Oversized piping systems add unnecessary construction costs, waste water and waste energy.

There’s also a potential health risk as oversized water pipes increase water aging and can foster the growth of pathogens such as legionella.

IAPMO created a Water Demand Calculator spreadsheet to estimate peak water supply demand for single- and multifamily residential dwellings.

The statistically-based methodology results in a 15 to 65 percent reduction in water demand estimates compared to the traditional Hunter’s Curve estimates.

Got questions? Contact Dan Cole  on our technical team.

IAPMO occasionally makes updates to the calculator and anticipates an app being available in 2021. Sign up below to receive updates:


Although care has been taken to ensure the accuracy, completeness and reliability of the Water Demand Calculator (“Calculator”), neither IAPMO nor any other party makes any warranties, express or implied, or representations as to the accuracy of the Calculator. Neither IAPMO nor any other party assumes any liability or responsibility for any error or omissions in the information contained in or output by the Calculator. Neither IAPMO nor any other party assumes any responsibility for the consequences of use of such information, nor for any infringement of third-party intellectual property rights which may result from its use.