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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 King County are safe. We also provide permitting and educational services for septic system owners, and septic professional certifications.
Short URL: kingcounty.gov/septic
Delays in service due to new permit system: Environmental Health Services has transitioned to a new permit system. Please have patience as we work through this transition time.
To create an account and get guidance on the system, see Public Health Permit Center.
Key septic resources
Search on-site sewage/septic system records
Online database with King County's official records.
Professionals who can help
Find information for professionals to work on your on-site sewage/septic system.
Financial assistance
Learn more about loans or grants for on-site sewage systems.
House or building remodels or expansions
Find the permitting steps for your remodels or expansions on septic systems.
Sales and transfers of properties with on-site sewage/septic systems
Learn considerations when buying or selling a property with a septic system.
Resources for different audiences
Resources for homeowners and residents
Information about septic maintenance, financial resources, property sales, and steps during construction/ remodels.
Resources for on-site sewage/septic system professionals
Detailed technical guidance, application information, certifications, and legal/ regulatory information
Resources for real estate professionals
Property sale information and other resources pertaining to real estate.
On-site sewage/ septic technical guidance
Drinking water
Public Health reviews applications for private water systems.
Applications and forms
Find wastewater applications and forms for the septic industry.
Resources to understand septic to sewer conversions
Find resources about septic systems in urban areas.
Revised on-site sewage system codes
King County revised the codes (rules) that govern on-site sewage systems (OSS) effective April 1, 2025.
Special projects
Equitable Wastewater Futures Program
Urban King County is home to nearly 40,000 OSS, many of which are past their intended life span and vulnerable to failure. The Equitable Wastewater Futures program works to identify the best wastewater treatment solutions for these properties.
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.