Sammamish, WA Landscaping Rules: Rainwater Harvesting (2026)

Washington was one of the first states to formally clarify that rainwater harvesting is allowed. In 2009 the Department of Ecology issued a policy stating that on-site storage and beneficial use of rooftop- or guzzler-collected rainwater is not subject to the water-right permitting process of Chapter 90.03 RCW. The key conditions are that the rainwater must be used on the property where it is collected and can only be collected from existing structures whose primary purpose is something other than collecting rainwater (a roof, for example). Approved non-potable uses include landscape irrigation, toilets/urinals, ornamental fountains and water features, cooling tower water, and car washing. Sammamish supports rainwater capture as part of low-impact development and stormwater management. While simple rain barrels need no permit, larger cisterns, systems that connect to indoor plumbing, or installations affecting building structure may require a building or plumbing permit, and using rainwater as a sole potable supply requires county/health approval. Because rainwater capture also reduces stormwater runoff, it can support compliance with the city's surface water management standards (SDC 21.03.050).