Septic permit rules and requirements in Washington
In Washington, the state sets the rule. The septic permit comes from your local health officer. For some systems the state issues it itself. The smallest tank allowed is 1,000 gallons. Washington Administrative Code § 246-272A-0005 · checked 2026-09-12
Wastewater Management Program
Writes the rules
checked 2026-09-23
Your local health officer
Issues the permit
checked 2026-09-12
Who decides a septic permit in Washington
Your local health officer issues an ordinary residential permit. For some systems the state issues it itself. The state sets the floor through the Wastewater Management Program, Washington State Department of Health.
The rule says both a local officer and the department run this chapter. A local officer issues most permits. The department issues permits for large systems only.
Washington Administrative Code § 246-272A-0005 · checked 2026-09-12
The office's phone number is 360-236-3330.
This is the general line for the Wastewater Management Program. The page also lists separate numbers for each topic and staff member.
Washington State Department of Health — Wastewater Management Program Contacts · checked 2026-09-23
The office publishes its own page on this: Washington State Department of Health — Wastewater Management Program.
The page names this address as its own canonical link.
Washington State Department of Health — Wastewater Management Program · checked 2026-09-23
What state law requires
Does Washington require a septic permit?
A permit is required to install, repair, modify, connect to, or expand an on-site sewage system. A minor repair needs no permit.
The local health officer decides whether to issue the permit.
Washington Administrative Code § 246-272A-0200 · checked 2026-09-23
The minimum septic tank size Washington allows.
1,000 gallons.
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
How far the drainfield must sit from a well in Washington.
100 feet.
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
How far a system must sit from the property line in Washington.
5 feet.
Applies to a tank, drainfield or reserve area, to a property or easement line.
Washington Administrative Code § 246-272A-0210 · checked 2026-09-23
Does Washington require an inspection when a home is sold?
Starting in 2027, an owner must have the system checked by an outside person at the sale.
A local health office may skip this if it already has proof the system passed.
Washington Administrative Code § 246-272A-0270 · checked 2026-09-23
Must the installer be licensed in Washington?
The local health officer must approve OSS installers, pumpers, and maintenance providers. Washington sets no separate state approval for them.
Each local office sets its own way to approve them. One office may accept another's approval.
Washington Administrative Code § 246-272A-0340 · checked 2026-09-23
What does an inspection cost in Washington?
These are prices, not permit fees. Each one comes from a government source.
$250 for an inspection.
Applies to the low end of the state's $250 to $400 range for a septic inspection.
The department asked local maintenance providers what fee they set for an inspection. A state rule requires one at a home sale after 2027.
Washington State Department of Health — Significant Legislative Rule Analysis, WAC 246-272A: On-Site Sewage Systems · checked 2026-09-23
Whether Washington counts what it permits
Yes. Washington publishes septic permit counts by county.
The page shows septic system counts for health departments in the Puget Sound area. It skips other counties, and it counts systems in place, not new permits.
Puget Sound Partnership — Puget Sound Info, "On-site sewage system compliance" · checked 2026-09-12
Counties with rules of their own
The state writes the code. Each county below adds rules of its own. Open the county to read them with their sources.
| County | Sets itself |
|---|---|
| King County | permit fee · inspection at sale · installer licensing |
| Snohomish County | permit fee · inspection at sale · soil log test holes · installer licensing |
| Whatcom County | permit fee · annual om fee · installer licensing |
Sources
State records only. Each figure above has a government source and a checked-on date. County figures live on the county pages.
- Washington State Department of Health — Wastewater Management Program
- Washington State Department of Health — Wastewater Management Program Contacts
- Washington Administrative Code § 246-272A-0005
- Washington Administrative Code § 246-272A-0010
- Puget Sound Partnership — Puget Sound Info, "On-site sewage system compliance"
- Washington State Department of Health — Significant Legislative Rule Analysis, WAC 246-272A: On-Site Sewage Systems
- Washington Administrative Code § 246-272A-0200
- Washington Administrative Code § 246-272A-0232
- Washington Administrative Code § 246-272A-0210
- Washington Administrative Code § 246-272A-0270
- Washington Administrative Code § 246-272A-0340
Verify before you act. Septic rules are set locally and they change. Check anything here with your local health officer before you spend money on it.