Septic rules and requirements in King County, Washington

Septic permits in King County are issued by the Public Health – Seattle & King County, On-Site Sewage/Septic System Program. A new system permit costs $731. USDA rates most of the soil in the county Very limited for septic absorption fields — 99.9% of the rated acres. Public Health – Seattle & King County — On-site sewage/septic system program · checked 2026-09-23

Public Health – Seattle & King County, On-Site Sewage/Septic System Program

Issues the permit

checked 2026-09-23

$731

Septic system permit

checked 2026-09-23

Very limited

USDA rating, 99.9% of rated acres

checked 2026-09-16

Who issues septic permits in King County?

Public Health – Seattle & King County, On-Site Sewage/Septic System Program, at 14350 SE Eastgate Way, Bellevue, WA 98007, 206-477-8050. It is part of county government. The state writes the rules it applies.

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

What does a septic permit cost in King County?

$731 for a septic system permit, on the county's own schedule.

Applies to a gravity system or a holding tank, the lower fee.

In effect from January 1, 2026.

The county's fee table for this permit
Gravity and Holding Tank system shown above	$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 does a replacement cost in King County?

These are prices, not permit fees. Each one comes from a government source.

$15,000 for a replacement.

Applies to the low end of the county's $15,000 to $40,000 range for a failed septic system.

The county publishes this range on its own septic rebate page. A working system costs far less to maintain than a failed one costs to fix.

King County — Septic System Maintenance and Side Sewer Repair Rebate Program · checked 2026-09-23

Is the soil in King County suitable for a septic system?

USDA rates most of the county Very limited for septic absorption fields — 99.9% of the rated acres. A rating describes the ground, not a parcel. The county's site evaluation decides each lot.

Very limited — 1,106,030 acres — 99.9% of 1,106,961 rated acres.
Somewhat limited — 931 acres — 0.1% of 1,106,961 rated acres.
Not rated — 51,998 acres, excluded from the denominator — mostly urban land and water.

USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-16

Does King County inspect a septic system when a house is sold?

The seller must hire an inspector to check the system before the sale closes.

King County Board of Health Code § 13.60.030, Operation and Maintenance at Time of Sale · checked 2026-09-23

What King County sets itself

The state writes the code. King County adds the rules below. They are what makes this page differ from the Washington requirements.

$731

Applies to a gravity system or a holding tank, the lower fee.

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
The seller must hire an inspector to check the system before the sale closes.

Applies to a sale or other transfer of property served by an on-site sewage system.

King County Board of Health Code § 13.60.030, Operation and Maintenance at Time of Sale · checked 2026-09-23
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

Sources

Each figure above has a government source and a checked-on date. USDA's Soil Data Access service supplies the soil records. A script writes them, and nobody types them.

Public Health – Seattle & King County — On-site sewage/septic system program · checked 2026-09-23
Public Health – Seattle & King County — About Environmental Health Services · checked 2026-09-23
King County Board of Health Code §§ 13.20.030, 13.20.035, 13.68 · checked 2026-09-23
Public Health – Seattle & King County — OSS Permitting, Certifications, and Drinking Water Fees, effective January 1, 2026 · checked 2026-09-23
Public Health – Seattle & King County — Search on-site sewage/septic system records · checked 2026-09-23
Washington Administrative Code § 246-272A-0232 · checked 2026-09-23
Washington Administrative Code § 246-272A-0210 · checked 2026-09-23
USDA NRCS Soil Data Access (SSURGO) · checked 2026-09-16
King County — Septic System Maintenance and Side Sewer Repair Rebate Program · checked 2026-09-23

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.