Bellevue, WA Landscaping Rules: Rainwater Harvesting (2026)

Rainwater collection, including the use of rain barrels, has become more popular as a supplemental source of water. In 2009, we issued a rainwater use interpretive policy , which clarifies that you may use water collected from your rooftop without a water right permit. However, there are rules on using rainwater as a potable (drinkable) water source. Some counties in Washington may allow rainwater collection for drinking water; however, many counties do not. Collected rainwater often has significant contaminants that must be removed before the water is considered safe for consumption. For regulation purposes, the Washington Department of Health’s Office of Drinking Water considers rainwater to be surface water subject to the requirements of the Surface Water Treatment Rule . If you want to use rainwater as your sole water supply when building a new home, contact your local county planning department. When does rainwater collection require a permit? Under our current policy, you don’t need a water right permit to collect rainwater, with a few conditions: Rainwater must be used on the property where it is collected. Rainwater can only be collected from existing structures that have another purpose other than collecting rainwater. If we find that rainwater collection is negatively affecting existing water rights in an area, local restrictions may be developed to govern new systems. However, we do not expect the collection of harvested rainwater to cause problems. If you are planning to use rainwater as your primary drinking water source for new building construction, you'll need to check with your county to see if it is allowed.