The following testimony was submitted by the Grassroot Institute of Hawaii for consideration by the Maui County Council’s Committee on Water and Infrastructure on Dec. 5, 2024.
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Dec. 5, 2024, 9 a.m.
Council Chamber
Kalana O Maui Building
To: Maui County Council’s Committee on Water and Infrastructure
Tom Cook, Chair
Yuki Lei Sugimura, Vice-Chair
From: Jonathan Helton, Policy Researcher
Grassroot Institute of Hawaii
RE: BILL 146 — A BILL FOR AN ORDINANCE AMENDING THE WATER CODE ON THE METHODOLOGY FOR CALCULATING DOMESTIC WATER DEMAND
Aloha Chair Cook, Vice-Chair Sugimura and other members of the Committee,
The Grassroot Institute of Hawaii supports the intent of Bill 146 (2024), which would replace the existing water fixture-unit methodology for calculating residential water use with a methodology based on daily estimated water use.
To assist with the daily estimated water use methodology proposed in the bill, Grassroot urges the Council to adopt the water-demand calculator created by the International Association of Plumbing and Mechanical Officials — the same organization that writes the model Uniform Plumbing Code.
This calculator is described in Appendix M of the 2018, 2021 and 2024 model plumbing codes,[1] and can be downloaded for free from the IAPMO website.
Current fixture-unit rules are based on the 80-year-old Hunter’s Curve, a graph used to determine the probability that water fixtures will be used at the same time.[2]
But this graph overestimates the likelihood of a “peak flow event” — like a football stadium at halftime. For single-family homes and apartments, the chances of such an event are low.
Overestimating the chances results in builders oversizing the piping for homes. Oversized piping increases the initial construction costs and lifetime water usage — therefore utility bills — when compared to the water demand calculator.[3]
Scrapping the outdated fixture-unit rules and replacing them with the new water-demand calculator could thus help facilitate the construction of more housing across the county.
And the need to change these rules is great.
As Grassroot pointed out in its recent brief, “How fixes to Maui’s water-fixture policy could ease its housing crisis,” the county’s water-uses rules are based on standards that have not been updated since 1995.
Water-using appliances have become more efficient since then, and IAPMO’s innovation has removed the need to rely on Hunter’s Curve.
It’s time to flush the old rules and bring Maui’s water policies into the 21st century.
Thank you for the opportunity to testify.
Jonathan Helton
Policy Researcher
Grassroot Institute of Hawaii
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[1] “Appendix M: Peak Water Demand Calculator,” 2024 Uniform Plumbing Code, IAPMO, p. 446.
[2] Judy Wohlt, “New Method Modernizes Hunter’s Curve Demand Estimates,” Working Pressure, Dec. 30, 2022.
[3] “Studies Detail the Cost Saving Potential of the Water Demand Calculator,” IAPMO, see Table 4A; and “Study: Water Demand Calculator™ Can Lead to Energy, Carbon and Water Savings in Single- and Multifamily Residences,” Contractor Magazine, June 13, 2023.
