State guide
Washington
Washington uses a local-health-jurisdiction model for most residential onsite sewage systems: county or district health agencies permit and manage systems up to 3,499 gallons per day. The state Department of Health sets and administers statewide rules, while larger systems shift to the state LOSS program or Ecology depending on flow and type.
Checked against official sources on October 4, 2026. Rules and links change; confirm with the office listed before you act.
- Who regulates septic permits
- Washington small onsite sewage systems are primarily regulated by local health jurisdictions, with the Department of Health administering statewide rules and the LOSS program for certain larger systems.
- Who can do the soil or perc test
- State rule says only professional engineers, designers, or local health officers may perform soil and site evaluations, and soil scientists may only perform soil evaluations.
- Licensed evaluators or designers
- Official page →
- State fee
- Not published by an official source we could verify. Ask the office.
Official resources in Washington
Explains whether the local health officer, DOH LOSS program, or Ecology has authority over a system.
Describes state and local roles, including the fact that local health jurisdictions permit and manage OSS in their counties.
State guidance on when to hire designers, engineers, installers, pumpers, and maintenance specialists.
Official state directory of county and district health jurisdictions residents use to find their local permit office.
Official Department of Licensing lookup for licensed designers and other professional licenses.
Key facts for Washington
- Local health jurisdictions permit and manage onsite sewage systems in their counties.
- For design flows from 0 to 3,499 gallons per day, the local health officer has authority and approval.
- For 3,500 to 100,000 gallons per day, the Department of Health LOSS program has authority and approval.
- Only professional engineers, designers, or local health officers may perform soil and site evaluations; soil scientists may only perform soil evaluations.
- Licensed Designers and Professional Engineers can design systems for new installations, alterations, and repairs.
- Washington does not publish one statewide small-OSS permit fee on the state pages reviewed; permit fees are typically local.
County septic and soil-evaluation offices in Washington
| County office | city | phone | Details |
|---|---|---|---|
| Thurston County Septic Systems Thurston County | Not published* | (360)-867-2669 | County septic program page with permitting resources, professional lists, and a septic help line. |
| Whatcom County Onsite Sewage Whatcom County | Bellingham | 360-778-6000 | County onsite sewage page for permits, records, licensed professionals, and environmental health contact. |
| Clallam County On-site Septic System Permits, Inspections & Education Clallam County | Not published* | 360-417-2258 | County program page for permits, inspections, online records, and homeowner training. |
| Snohomish County Health Department Septic Permitting Snohomish County | Everett | 425-339-5250 | County health department page for design application review, installations, certifications, complaints, and permit steps. |
| Kitsap Public Health Drinking Water & Onsite Sewage Kitsap County | Bremerton | 360-728-2235 | District page for septic applications, certified professionals, records, maintenance, and technical assistance. |
* Not published: the official page doesn't list it. Call the office to confirm before you rely on it.
What to do next
- Find your county or district health agency first; that local office is usually the actual permit issuer for a home septic project.
- Hire a licensed designer or professional engineer early if you need a new system, alteration, or repair design.
- Ask your local health jurisdiction whether it also requires local certification or approval for installers, pumpers, and maintenance specialists.
Not seeing your county office or county?
Not every county office publishes its rules online. Try these, in order:
- General Start with the statewide information above.
- Closest verified Nearest places where we have verified local data outside this state (distance from Washington's population center, for comparison only):
- Clackamas County Septic and Onsite Wastewater Program, Oregon · about 148 miles
- Clackamas County How to Apply for a Permit: Septic, Oregon · about 148 miles
- Panhandle Health District — Benewah County Environmental Health, Idaho · about 225 miles
- Call to confirm Ask the official office.Management Roles for On-site Sewage Systems
Website →Phone: (360) 236-3330 (as listed on that page, checked Oct 4, 2026)Your city or county office: MRSC Washington city and town profiles →Not sure who handles it locally? USAGov's free help line, 1-844-872-4681, or the Washington page on USA.gov can point you to the right office. - Know the current info? Tell us with a link to the official page.