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Beckoning Cister/Vine Street.
Photo: Buster Simpson
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What is Rainwater Harvesting?
Rainwater harvesting is the capture and storage of rainwater for beneficial use. Rainwater is considered the cleanest form of harvested water and ca n be used for toilet flushing, hose bibs, industrial applications, domestic clothes washing, irrigation, water features and other approved usages.
Rainwater harvesting can be an important green building strategy, and can contribute towards credits in both the LEED™ standard and Built Green™ program. For example, rainwater harvesting can help a project achieve stormwater quantity, water efficient landscaping, innovative wastewater technologies, water use reduction and innovation in design credits in the LEED standard. For more information on LEED visit www.usgbc.org, and Built Green visit www.builtgreen.net.
Why harvest rainwater?
Rainwater harvesting provides many benefits. It can generate savings by reducing utility fees charged for potable water use and sanitary sewer use. It protects our local water bodies such as the Puget Sound, Lake Union and Lake Washington by reducing combined sewer overflows during peak storm events. And, rainwater harvesting conserves water by reducing demand for potable water that is used for non-potable purposes.
What are the requirements for Rainwater Harvesting?
Plumbing and Public Health Requirements
The City of Seattle partnered with Seattle King County Public Health to develop rainwater harvesting policy and procedures titled, Rainwater Harvesting and Connection to Plumbing Fixtures. The policy addresses rainwater harvesting systems with connection to plumbing fixtures in structures. It provides design guidelines and addresses specific regulatory requirements and procedures for commercial and residential rainwater harvesting systems, including system components. For more information contact Seattle King County Public Health at 206-296-4600.
Stormwater Code Requirements
Seattle Public Utilities (SPU) is currently revising the Stormwater, Grading and Drainage Code. The Proposed Revisions to Stormwater Code and Draft Director's Rules address how rainwater harvesting can be paired with detention cisterns. The new code does not allow rainwater harvesting to count toward detention volume, but does offer guidance as to how the two types of systems can be complimentary. Rainwater cisterns are addressed in the Draft Director's Rules, Volume 3 Stormwater Flow Control and Water Quality Treatement.
How is Seattle promoting Rainwater Harvesting?
Client Assistance Memo
To provide additional technical and regulatory guidance, DPD published Client Assistance Memo (CAM) 701, Rainwater Harvesting for Beneficial Use. The CAM provides definitions, explains the benefits of rainwater harvesting, and offers suggestions on system components, requirements and design considerations. also features both a commercial and residential case study that includes the rainwater system design components. CAM 701 can be obtained online or at DPD’s Applicant Service Center at 700 Fifth Avenue, Suite 2000, Seattle.
Water Right Permit
SPU received a water right permit from the Washington State Department of Ecology to capture and use rainwater that falls on rooftops and structures in areas of the City that have combined and partially combined drainage and sewer system. The water right permit clears the way for property owners by removing legal uncertainty. SPU plans to develop initiatives that will encourage and hasten adoption of rainwater harvesting. Rainwater harvesting helps SPU protect the environment and more sustainably manage natural resources by reducing peak stormwater flows that enter Seattle’s combined drainage and sewer system, and conserving potable water currently used for non-potable purposes. Visit SPU’s Rainwater Permit webpage for a map of combined and partially separated sewer neighborhoods and additional information regarding the water rights program, or contact Paul Fleming at paul.fleming@seattle.gov or 206-684-7626.
Natural Gardening and Rain Barrel Program
SPU also encourages homeowners to install rain barrels as part of the Natural Gardening and Rainwater Harvesting Program. Rain barrels allow residents to use the collected rainwater to water landscapes during dry summer months, and reduce potable water use for landscape irrigation needs.
Are there incentives for Rainwater Harvesting?
Lower Drainage Fees
Property owners can apply for a 10% credit on their drainage fee. For more information about savings on drainage fees contact Timothy Lowry at timothy.lowry@seattle.gov or 206-684-4150, or contact SPU Customer Service at 206-684-3000.
Financial Incentives for Businesses and Industrial Facilities
Another source of incentives for businesses and industrial facilities is through the Saving Water Partnership funded by SPU and other local utilities in King County. For more information contact Phil Paschke, 206-684-5883 or Phil.Paschke@Seattle.gov.
Seattle Green Factor Bonus
The Seattle Green Factor requires new development in neighborhood business districts to meet a landscaping target using a menu of landscaping strategies. The Green Factor is designed to improve the extent and quality of landscapes, while allowing greater flexibility for developers and designers to meet open space requirements. It encourages layering of vegetation in areas visible to the public and along streets adjacent to new development.
When used for landscape irrigation, rainwater harvesting can provide bonus credits for the Green Factor landscaping requirement. A series of worksheets help applicants calculate their project’s score, allowing them to try different combinations of features to reach the requirement, including the Green Factor Worksheet; Planting Area Calculation worksheet; and Rainwater Harvesting Calculation Tool.
Are there examples of Rainwater Harvesting Systems?
Seattle Case Studies
The City of Seattle has a number of case studies of city-funded green building projects that incorporated rainwater harvesting systems, including:
Other case studies within Seattle:
Additional Rainwater Harvesting Resources
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