WA septic O&M by county

Short county checklists for Washington septic owners: inspection intervals, whether homeowner self-inspect is allowed, training links, and where reports go. County rules gate everything. Hire a licensed professional when your local health jurisdiction requires it.

State baseline (then check your county)

• Gravity (septic tank + gravity drainfield only): inspect at least every 3 years.
• All other systems: inspect at least annually, unless the LHJ or manufacturer requires more often.
• Self-inspect is allowed only if your local health department authorizes it (often after training/certification). Do not invent a DIY path.
• Property transfer: statewide third-party inspection rules phase in beginning February 1, 2027 under WAC 246-272A. Some counties already run their own sale/transfer programs — use the county page.

County pages

• Pierce

  3-year simple / annual complex. DIY path exists (WOSSA + TPCHD eligibility). OnlineRME reports.

  Pierce checklist →

• King

  Title 13 intervals by system type. Time-of-sale needs a licensed maintainer. OnlineRME / SkipThePaper.

  King checklist →

• Thurston

  Operational certificates + free self-inspect certification for qualifying systems. OnlineRME.

  Thurston checklist →

• Kitsap

  3-year typical / annual alternative with maintenance contract. Homeowner M&M certification path via WOSSA.

  Kitsap checklist →

• Snohomish

  3-year gravity / annual alternative. Hire certified Monitoring & Maintenance specialists. OnlineRME lookup.

  Snohomish checklist →

• Whatcom

  3-year gravity / annual other. Free HOST training for eligible homeowner evaluations. HROSS report path.

  Whatcom checklist →

Before you start

• Confirm which county health jurisdiction covers the parcel (not just the mailing city).
• Look up your system type / as-built before assuming “gravity = DIY.”
• Pumping is not the same as an O&M inspection.
• Gear shopping is optional — see the gear checklist. Accessories do not replace a required inspection.