Hawaii County, HI Landscaping Rules: Rainwater Harvesting (2026)
Key Facts
- Permit trigger
- Any water tank or catchment, § 5-3-1(b)(7)
- No-permit irrigation lane
- Exterior catchment up to 360 gallons, § 5F-2-1
- Single-family exemption
- Exterior catchment plumbing components exempt
- Other permits still apply
- Electrical, tank-support, and enclosure work
- ADU water source
- Rain catchment allowed, § 25-6-30
- Unpermitted work penalty
- Civil fine up to $1,000 per day
Summary
Hawai'i County treats a catchment tank like any other plumbing fixture: Section 5-3-1(b)(7) requires a permit to install, alter, remove, or replace a water tank or catchment used for potable, household, or fire-protection water, no matter its size. The county's 2012 Uniform Plumbing Code amendment then opens a narrow no-permit lane for small exterior irrigation systems and single-family exterior components.
1601.3 Permit or Approval. It shall be unlawful for any person to construct, install, alter, or cause to be constructed, installed, or altered any alternate water source system in a building or on a premises without first obtaining a permit or approval to do such work from the Authority Having Jurisdiction. Exceptions: (1) A permit is not required for exterior rainwater catchment systems used for outdoor drip and subsurface irrigation with a maximum storage capacity of 360 gallons (1363 L). (2) A plumbing permit is not required for rainwater catchment systems for single family dwellings where outlets, piping, and system components are located on the exterior of the building. This does not exempt the need for permits where required for electrical connections, tank supports, or enclosures.
Full Breakdown
3 of the 2012 Uniform Plumbing Code to spell out the exceptions homeowners actually use: no permit is required for an exterior rainwater catchment system feeding only outdoor drip or subsurface irrigation up to 360 gallons of storage, and a plumbing permit specifically is not required for a single-family rainwater catchment system whose outlets, piping, and components stay on the building's exterior, though electrical, tank-support, and enclosure permits can still apply to that same system. Catchment water is not just an irrigation option here: Section 25-6-30 lists a rain catchment system, alongside a public water system, private water system, or well, as an acceptable potable water supply for an accessory dwelling unit, subject to the director's approval and State Department of Health requirements when systems are combined.
Every catchment installation still falls under the construction code's administrative rules in Chapter 5, meaning the same plan review, fee schedule, and inspection process that applies to any other plumbing permit, and unpermitted catchment work is enforced exactly like unpermitted plumbing work under Sections 5-10-1 through 5-10-3.
Violations & Fines
Skipping the tank or catchment permit is enforced the same way as any other plumbing violation. Section 5-10-1(4) makes unpermitted plumbing work a violation of the construction code, and the director can issue a Section 5-10-2 administrative order carrying a civil fine up to $1,000 plus up to $1,000 per day the violation continues, appealable to the board of appeals within thirty days. Section 5-10-3 allows criminal referral as a petty misdemeanor, up to $1,000 and thirty days in jail per day of violation.
Frequently Asked Questions
Do I need a permit to install a rainwater catchment tank in Hawai'i County?
Is any size of catchment system exempt from the permit?
Can catchment water be my only water supply for an ohana or ADU?
What happens if I install a catchment tank without a permit?
Sources & Official References
Other rules in Hawaii County
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