Yes, rainwater collection is legal in Washington, but subject to specific restrictions under state and local water rights laws.
Washington permits rainwater harvesting for non-potable uses, such as irrigation or toilet flushing, without requiring a water right permit if the system is designed for on-site use and does not exceed 5,000 gallons of storage. However, collection for potable purposes or diversion to off-site properties triggers state water rights enforcement under the Washington State Department of Ecology (Ecology). Local jurisdictions, including Seattle Public Utilities and Spokane County, may impose additional permitting requirements for larger systems or commercial installations. Recent 2026 compliance shifts emphasize stormwater management integration, requiring systems to align with local drainage codes to avoid penalties.
Key Regulations for Rainwater Collection in Washington
- Water Rights Compliance: Ecology enforces prior appropriation doctrine; unpermitted diversions for consumptive use violate RCW 90.03.010. Small-scale non-consumptive systems (e.g., <5,000 gallons) are typically exempt under Ecology’s 2023 guidance.
- Local Permitting: Municipalities like King County require permits for systems exceeding 1,000 gallons or connected to potable water supplies. Seattle’s 2024 Stormwater Code mandates filtration for rainwater used in green infrastructure projects.
- Health and Safety Standards: Potable systems must meet Washington Administrative Code (WAC) 246-290-490 standards, including filtration and disinfection, enforced by local health departments. Cross-connection risks with municipal supplies are strictly prohibited.