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On-site sewage/septic system program

The Public Health – Seattle & King County On-site Sewage/Septic System Program helps make sure that over 85,000 sewage/septic systems in Seattle are safe. Sewage/septic systems treat wastewater when homes and buildings are not connected to public sewer systems. We also provide permitting and educational services for owners of septic systems, and certifications for some septic professionals.

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OSS code revision process

King County is updating our local OSS codes to make sure they comply with recent changes to state codes. This is also an opportunity to make changes to improve OSS regulations in King County. Learn more about this process, including possible code revisions, upcoming public meetings, and how you can make your voice heard on our code revision website. We have a code revision survey that is open until Aug. 15, and public meetings on July 27 and August 8.

Resources for homeowners and residents

Find sewage/septic information for homeowners and residents.

Resources for on-site sewage/septic system professionals

Professionals need Certificates of Competency to work on and maintain septic systems. Learn more about becoming certified or renewing your certification.

Resources for real estate professionals

Find sewage/septic information pertaining to real estate.

Search on-site sewage/septic system records

The online database has King County's official records. You can also find the record drawing search utility, King County iMap, and other resources.

Maintaining your on-site sewage/septic system

Sewage/septic system owners need to have their system inspected regularly. Learn more about proper sewage/septic system care.

Financial assistance

Learn more about loans or grants for on-site sewage systems.

Property sales and transfers

Find information for buyers and sellers of properties with on-site sewage/septic systems. Buyers and sellers both have responsibilities during a sale.

Applications and permits

You must have a permit to install, repair, or replace an on-site sewage/septic system. Find more information about permits and applications.

On-site Sewage System Technical Advisory Committee

The On-site Sewage/Septic System (OSS) Technical Advisory Committee brings together industry partners and impacted parties to participate in OSS policy development and problem resolution.

Healthy beach project

Learn how the Vashon-Maury Pollution Identification and Correction Project helps you, and how you can help.

Marine Recovery Area

Learn about the importance of a Marine Recovery Area, the areas impacted, and how it affects you.