Skip to main content
CityRuleLookup
🌿 Landscaping Rules/Rainwater Harvesting

Rainwater Harvesting: Honolulu vs Mililani Mauka

How do rainwater harvesting rules compare between Honolulu, HI and Mililani Mauka, HI?

Honolulu and Mililani Mauka have similar restriction levels.

Honolulu, HI

Honolulu County

Few Restrictions

Honolulu County has no ordinance restricting residential rainwater harvesting; the Board of Water Supply encourages it countywide through a rain barrel rebate program and CTAHR catchment guidelines.

View full Honolulu rules β†’

Mililani Mauka, HI

Honolulu County

Few Restrictions

Mililani Mauka homeowners may install rain barrels without a Honolulu permit; small outdoor catchment up to 360 gallons is exempt under state plumbing code.

View full Mililani Mauka rules β†’

Key Facts Comparison

FactHonoluluMililani Mauka
County ordinanceNone-
Permit thresholdUp to 360 gallons exempt-
Rebate programBoard of Water Supply-
GuidelinesUH CTAHR catchment program-
State restrictionsNone-
City code-No specific ordinance
Plumbing code-Up to 360 gallons exempt
Incentive-BWS rebate programs
HOA layer-Mauka design review

Highlighted rows indicate differences between cities.

Honolulu FAQ

Do I need a permit for a backyard rain barrel on Oahu?

Usually no. Exterior catchment up to 360 gallons for outdoor irrigation is exempt under the Hawaii Plumbing Code, and Honolulu County has no separate ordinance.

Are there incentives for catching rainwater?

Yes. The Honolulu Board of Water Supply runs a rain barrel rebate program encouraging conservation. Details and eligibility are posted on the BWS website.

Mililani Mauka FAQ

Do I need a permit for a rain barrel in Mililani Mauka?

No. Residential catchment under 360 gallons is exempt under the Hawaii Plumbing Code, and Honolulu has no specific residential catchment ordinance.

Will the Mauka HOA let me install a rain barrel?

Usually yes with screening. Submit your plans to the Mililani Mauka Community Association architectural review to confirm placement and color requirements.

Compare other topics

See how Honolulu and Mililani Mauka compare on other ordinance categories.

Want to add a third city?

Use our full comparison tool to compare up to three cities.

Open Comparison Tool