The following commentary was originally published July 16, 2026, in The Garden Island under the headline “New rainwater catchment law could boost housing stock.”
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The Hawaiʻi Legislature passed a bill this year that now allows folks across the state to install rainwater catchment systems.
HB1728, which took effect July 1, is a victory for anyone who is interested in building new housing but unable to connect to the water system in their county.
This new law supersedes certain county regulations, such as the Kauai Department of Water’s rules that do not allow catchment systems anywhere that is already served by county water lines.
As I explained in a column last year (“Kauai lawmakers should revisit rain catchment,” Sept. 20, 2025), this was a problem because water catchment systems were off limits even in areas where the county’s water system is operating at maximum capacity.
That situation has prevented many Kauai homeowners from building backyard cottages or farm dwellings because they could neither connect to the county water system nor install their own catchment systems to supply water to new living areas.
The county’s limited water infrastructure and water catchment regulations have also delayed at least one housing project.
The Waipā Foundation has been planning for several years to build employee housing units — in addition to other facilities to support its community and economic development initiatives — on 1,600 acres it manages near Hanalei.
But in April, the foundation’s executive director, Stacy Sproat, told state senators that “until something changes” with the county’s water catchment regulations, its proposed project is “dead in the water.”
“The Kaua`i [Department of Water] has informed us that the Hanalei system does not have capacity to support our project, and regulations do not currently permit another potable water system on a property with an existing county meter,” Sproat explained.
HB1728 now requires the counties to allow water catchment systems on all properties, even ones that supposedly have access to county water systems.
It does, however, allow the counties to register or inspect private catchment systems to mitigate possible public health issues, although they are not mandated to do so.
A representative of Hawaiʻi Farmers Union United also testified in favor of the bill.
Hunter Heaivilin, the organization’s advocacy director, said that allowing rainwater catchment systems on all properties, for both potable and nonpotable uses, “empowers farmers and residents alike to harness an abundant and renewable resource.”
That resource — rain — could expand housing opportunities throughout the state, even as drought conditions become more frequent in some areas. Kauai, for example, experienced 85% less rain in 2025 than its historical average.
Ryan Kanaka‘ole, acting chair of the the state Department of Land and Natural Resources, wrote in testimony that the department’s Commission on Water Resource Management “encourages the use of alternative water sources, including reuse, wastewater, stormwater, and rainwater catchment,” to help address the concern that current and future droughts could deplete stream and well water resources.
For many reasons — housing, agriculture and even the environment — this new law is a win.
