Using Harvested Rainwater Outdoors vs. Indoors
Harvested rainwater is often used for outdoor irrigation, such as watering a lawn or garden. In Portland, you are not required to get a city building permit to harvest rainwater and use it outdoors if harvested rainwater is intended for irrigation only and the system is completely separate from the municipal water system. However, other permits, such as an electrical permit for any pumps installed or a grading permit for underground pipe installation, may be necessary depending upon system size and complexity.
Most rainwater harvesting systems in Portland designed for indoor water use are for nondrinking water uses such as flushing a toilet. If thinking about harvesting rainwater for limited, residential indoor use, follow the relevant Code Guide for rainwater harvesting available through the Bureau of Development Services.
Learn about local plumbing code requirements for harvesting rainwater by reading the specialty plumbing code: Chapter 6: Rainwater Harvesting Systems for Interior Use or Combined Interior and Exterior Use.
Rainwater harvesting systems can play a part in on-site stormwater management. Handling stormwater on your property by disconnecting downspouts, building rain gardens, or installing rain barrels can help reduce combined sewer overflows (CSOs), increase groundwater recharge, and reduce pollutants in surface waters. Rainwater harvesting systems can also be used during new construction or redevelopment to address stormwater management requirements and to help projects meet green building certifications.
The Bureau of Environmental Services has a variety of publications available to help Portlanders manage stormwater. Visit the Sustainable Stormwater section of their website for more information.
When you manage stormwater runoff on you property you can qualify for a discount of up to 100% of the on-site stormwater charge that appears on your water bill. Learn more about Clean River Rewards by visiting www.cleanriverrewards.com or by calling 503-823-7740.
The benefits of harvesting rainwater vary widely from climate to climate. Rainwater can be used for outdoor irrigation, indoor non-potable (non-drinking water) uses, or potable uses with treatment. Portland receives around 37 inches of rainfall annually. However, 90% of this rainfall happens from October to May – a time of year when gardeners aren’t looking for supplemental water for their lawns or gardens. Because of this seasonal pattern, it is important to thoughtfully consider what harvested rainwater is to be used for, and determine landscape water needs if planning to use it outdoors.
The majority of Portland’s drinking water comes from the Bull Run watershed - an area of land that drains about 102 square miles of forested landscape. Plenty of rain falls on the Bull Run watershed, averaging 130 inches per year. The heaviest rains occur from late fall through spring and are important for filling the two reservoirs in the watershed. Water stored in the reservoirs during the winter is essential for meeting summer water demand.