Short definition
A septic system inspection is a certified review of the tank, baffles, effluent filter, distribution box, drainfield surface, and alarm. In Washington, WAC 246-272A-0270 requires routine inspection at least every three years for gravity systems and annually for ATU, mound, sand filter, and pumped systems. A separate property-transfer inspection becomes mandatory statewide on February 1, 2027.
What it is
A WA-certified maintainer or third-party inspector visits the property and works through a standard checklist: tank lid access and condition, sludge depth, scum thickness, baffle integrity, effluent filter cleaning, distribution box level and split, surface condition over the drainfield, signs of breakout, alarm function on pumped or aerobic systems, and reserve-area encroachment.
The inspector files a maintenance report with the local health jurisdiction on an approved form. For routine 3-year inspections, the homeowner usually arranges this through the same company that pumps the tank. For property-transfer inspections, a third-party authorized inspector must perform the work — the maintainer who services the system can’t sign their own sale-time report.
Why it matters to a homeowner
A skipped inspection is the easiest way to lose a drainfield. A clogged effluent filter or a tipped distribution box pushes solids into the field; once the soil’s biomat fails, the only fix is a full drainfield replacement at $15,000–$30,000+. The inspection itself is cheap insurance.
For sellers, the 2027 transfer rule turns inspection into a closing-table item. A failed system can stop a sale or force tens of thousands in escrow. For buyers of any septic property in 2027 or later, the report is the single most important document in the transaction — read it before you sign.
When you’ll encounter this term
- Routine maintenance every 3 years (gravity) or annually (ATU, mound, sand filter, pumped).
- Listing or buying a property with a septic system on or after February 1, 2027.
- Inheriting an unfamiliar system — a baseline inspection in the first year is cheap clarity.
- A septic alarm sounds and the service tech recommends a full system check.
- Building an addition or planting near the drainfield — confirm the reserve area.
Cost and what to expect
- Routine 3-year inspection: $200–$400 in most WA counties.
- Property-transfer inspection: $245–$500. Snohomish County set its fee at $245 for 2026–27, rising to $255 for 2027–28.
- Pumping is a separate service: $300–$600.
- A typical inspection runs 60–90 minutes. Have the tank lid accessible and the maintenance log handy.
Common findings
- Sludge or scum exceeding the pumping threshold — schedule a pump-out.
- Effluent filter missing or clogged — clean or install one.
- Distribution box no longer level — relevel so each lateral gets equal flow.
- Drainfield surface wet or unusually green — possible breakout.
- Reserve area encroached by a shed, garden, or driveway — a closing-table problem starting 2027.
- Alarm non-functional on a pumped or ATU system.
Washington note
Washington’s WAC 246-272A-0270 sets the inspection cadence statewide, and WAC 246-272A-0260(5) adds the property-transfer inspection rule effective February 1, 2027. Implementation runs through each county health jurisdiction, and details are still rolling out in 2026:
- King County already requires a pre-transfer inspection by a certified on-site maintainer through Public Health – Seattle & King County.
- Pierce County uses a Report of System Status (RSS) through TPCHD before sale.
- Snohomish County has its ordinance aligned with the 2027 statewide rule and its fee schedule published.
- Mason, Jefferson, Kitsap, Clallam, Skagit counties — high-septic-density jurisdictions — are finalizing their forms and authorized-inspector lists.
If you’re listing a septic property in 2026, schedule the transfer inspection 30–60 days before closing and confirm the inspector’s authorization with your county health department first.