Yes, rainwater collection is legal in Hawaii, but subject to strict permitting and usage restrictions under state water laws and county ordinances. While not outright banned, compliance with Hawaii’s water rights framework and county-specific rules is mandatory to avoid penalties.
Key Regulations for Rainwater Collection in Hawaii
- Water Rights Compliance: Collection requires approval from the Hawaii Commission on Water Resource Management (CWRM) if diverting more than 100,000 gallons annually or impacting stream flow, per Hawaii Revised Statutes §174C-30. Small-scale residential use (e.g., <10,000 gallons/year) typically exempts homeowners from permits but not from county oversight.
- County-Specific Ordinances: Honolulu, Maui, and Hawaii County impose additional rules. For example, Maui County’s Water Use and Development Plan (2023) mandates rainwater harvesting systems meet Department of Water Supply standards, while Hawaii County’s Code of Ordinances §13-101 restricts commercial-scale collection without a water use permit.
- 2026 Compliance Shifts: The CWRM’s Water Resource Protection Plan (effective 2026) will tighten reporting requirements for all collection systems, including mandatory metering for systems exceeding 5,000 gallons/month. Non-compliance risks fines up to $10,000 under HRS §174C-41.
Local agencies enforce these rules variably; consult the CWRM and county water departments before installation. Off-grid systems in rural areas face fewer restrictions but must still adhere to state water quality standards if used for potable purposes.