Washington Allows Rooftop Rainwater Harvesting Without Permit

Under RCW 90.03.260 and Department of Ecology Policy 1017, rooftop rainwater harvesting from existing structures for onsite beneficial use is allowed statewide without applying for a water right. The 2009 policy clarifies that catchment from impervious surfaces such as roofs is exempt from water-right permitting. Cities cannot prohibit residential rooftop collection, although they may impose reasonable plumbing, cross-connection, and building code requirements consistent with the Uniform Plumbing Code adopted under RCW 19.27.031.

Improper plumbing connections may trigger building code enforcement, but no permit is required for typical residential rooftop systems.