Renton, WA Landscaping Rules: Rainwater Harvesting (2026)

Washington state generally allows rooftop rainwater collection without a water right under Department of Ecology policy (POL-1017, 2009) and WAC 173-500 guidance. This applies statewide including Renton. Rainwater harvested from rooftops can be used for outdoor irrigation, toilet flushing, laundry, and (with treatment) potable uses under the Washington State Building Code Appendix O and RCW 19.27. Systems using harvested rainwater for potable water require WA Department of Health review. Renton Community and Economic Development encourages rain barrels and cisterns as part of the city's stormwater management goals under RMC 4-6-030 (Drainage Standards). Rain barrels under 200 gallons generally need no permits. Cisterns over 5,000 gallons or those connected to plumbing systems require building and plumbing permits. Rainwater systems qualify for stormwater credits in some new developments under the Renton Surface Water Design Manual (based on the 2021 King County Surface Water Design Manual). Harvested rainwater is particularly valuable for summer garden irrigation given Puget Sound's dry-summer Mediterranean climate. Cross-connections to potable water must have backflow prevention. Overflow should infiltrate on site or direct to vegetated areas, not storm drains.