Septic permits and fees in King County, Washington
A septic system permit in King County costs $731. The county sets that fee in its own schedule. Public Health – Seattle & King County, On-Site Sewage/Septic System Program issues the permit. State rules fix the tank floor at 1,000 gallons. A private well needs 100 feet from the drainfield, a property line 5 feet. Public Health – Seattle & King County — OSS Permitting, Certifications, and Drinking Water Fees, effective January 1, 2026 · checked 2026-09-23
$731
Septic system permit
checked 2026-09-23
1,000 gallons
Tank floor, state rule
checked 2026-09-23
100 feet
Drainfield to a well
checked 2026-09-23
Which septic permit applies in King County?
The septic system permit, and it starts with the site evaluation. A licensed on-site sewage system designer must complete a soil and site evaluation. Washington does not use a percolation test. The permit follows a passing evaluation. The building permit follows the septic permit.
The designer records soil type, depth to water, and other site conditions on soil logs. King County requires at least four soil logs for a single-family lot.
King County Board of Health Code § 13.28.020, Design Support Materials · checked 2026-09-23
What are the current septic fees in King County?
$731 for a septic system permit, on the county's own fee schedule.
Applies to a gravity system or a holding tank, the lower fee.
In effect from January 1, 2026.
| Gravity and Holding Tank system | $731 | a system the source lists as gravity system or holding tank; whichever applies, the lower fee |
|---|---|---|
| Pressurized system | $1,181 | a system the source lists as pressurized system |
This is the design review fee, paid when the septic design is submitted. A pressurized system costs more to review. A separate fee applies later for the installation permit. The state code sets no fee amount.
Public Health – Seattle & King County — OSS Permitting, Certifications, and Drinking Water Fees, effective January 1, 2026 · checked 2026-09-23
What state law fixes for every Washington system
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1,000 gallons minimum septic tank capacity
Applies to a house with four bedrooms or fewer.
See Table VII for homes with more than four bedrooms.
Washington Administrative Code § 246-272A-0232 · checked 2026-09-23
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100 feet from a private well to the drainfield
Applies to a drainfield or reserve area, measured to a well.
The setback from the sewage tank to a well is shorter.
Washington Administrative Code § 246-272A-0210 · checked 2026-09-23
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5 feet from any property line
Applies to a tank, drainfield or reserve area, to a property or easement line.
Washington Administrative Code § 246-272A-0210 · checked 2026-09-23
What King County requires that the state does not
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King County licenses septic installers, maintainers, and pumpers. Each one passes an exam. Installers and maintainers also post a bond.
Applies to a licensed septic worker in King County.
Washington tells every county to set up this approval system. It does not set the exam, the bond, or the renewal date. King County sets all three in its own code.
King County Board of Health Code §§ 13.20.030, 13.20.035, 13.68 · checked 2026-09-23
Where do you file the application with Public Health – Seattle & King County, On-Site Sewage/Septic System Program?
Public Health – Seattle & King County, On-Site Sewage/Septic System Program, 14350 SE Eastgate Way, Bellevue, WA 98007, 206-477-8050.
This is the Bellevue office line for wastewater and septic questions. Call during the posted phone hours.
Public Health – Seattle & King County — On-site sewage/septic system program · checked 2026-09-23
The steps, in the county's order
- Hire a state-licensed on-site sewage system designer. The designer completes a soil and site evaluation and designs the system.
- The designer submits the design to Public Health. The design review fee is due with it.
- Public Health reviews the design. An approved design stays valid for three years, or until a building permit is issued.
- A certified master installer applies for the permit and pays the fee.
- Once the system is built, the designer checks it before it is covered. The designer tells the county it is ready.
- Public Health has 10 working days to approve or deny the finished system.
King County Board of Health Code § 13.28.020, Design Support Materials · checked 2026-09-23
How do you get a copy of your septic permit record in King County?
Ask Public Health – Seattle & King County, On-Site Sewage/Septic System Program for the permit record for the property. Call 206-477-8050 or start at its website.
Public Health – Seattle & King County — On-site sewage/septic system program · checked 2026-09-23
Search on-site sewage/septic system records
This tool finds site designs and past inspection reports for a property. It covers many years of records.
Public Health – Seattle & King County — Search on-site sewage/septic system records · checked 2026-09-23
Sources
Each figure on this page has a government source and a checked-on date.
- Public Health – Seattle & King County — On-site sewage/septic system program
- Public Health – Seattle & King County — About Environmental Health Services
- King County Board of Health Code §§ 13.20.030, 13.20.035, 13.68
- Public Health – Seattle & King County — OSS Permitting, Certifications, and Drinking Water Fees, effective January 1, 2026
- Public Health – Seattle & King County — Search on-site sewage/septic system records
- Washington Administrative Code § 246-272A-0232
- Washington Administrative Code § 246-272A-0210
- USDA NRCS Soil Data Access (SSURGO)
- King County — Septic System Maintenance and Side Sewer Repair Rebate Program
Verify before you act. Septic rules are set locally and they change. Check anything here before you spend money on it. Call the Public Health – Seattle & King County, On-Site Sewage/Septic System Program, on 206-477-8050.