Septic inspection requirements by system type
Washington sets two inspection frequencies, and which one applies to you depends entirely on what kind of system you own. Most owners who get this wrong assume the three-year rule covers them when it does not.
The two frequencies
| System type | Inspection frequency | Who performs it |
|---|---|---|
| Sewage tank with a gravity subsurface soil absorption system, and nothing else | At least once every three years | Third party authorized by the local health officer |
| Every other on-site sewage system type, including pressure distribution, sand filters, mounds and proprietary treatment units | Annually | Third party authorized by the local health officer |
Source: WAC 246-272A-0270, read 2026-09-18.
Working out which system you own
The as-built drawing on file with the Health Department is the definitive answer. It shows the components that were installed and where they sit.
A pump chamber, an electrical panel or alarm for the septic system, a sand filter, a raised mound in the yard, or a manufacturer name anywhere in the paperwork. Any of these means the system does more than settle and disperse, and the annual requirement applies.
A tank and a gravity-fed drainfield, no pump, no alarm, no treatment unit. Common on the fast-draining outwash of the Graham, Spanaway and Roy prairies where gravity distribution works.
Assume the shorter interval and ask an inspector at the first visit. Being early costs one inspection fee. Being late leaves a gap in the maintenance record that shows up at sale.
Everything WAC 246-272A-0270 puts on the owner
- Owners must operate, monitor and maintain an on-site sewage system to minimize the risk of failure.
- A system consisting solely of a sewage tank and a gravity subsurface soil absorption system must be inspected at least once every three years, unless the local health officer specifies more often.
- All other on-site sewage system types must be inspected annually, unless the local health officer specifies more often.
- Those inspections must be obtained from a maintenance service provider authorized by the local health officer, and the results submitted to the local health jurisdiction on a form the local health officer approves.
- At the time of property transfer, and this part applies now, the owner must give the buyer all available maintenance and repair records, in addition to the seller disclosure statement required by chapter 64.06 RCW for residential real property.
- Beginning February 1, 2027, the owner must also obtain a property-transfer inspection from a third-party inspector authorized by the local health officer, plus an inspection of any proprietary treatment products per the manufacturer recommendations, and submit the results on an inspection report form the local health officer approves.
- The local health officer may remove the transfer-inspection requirement where the local health jurisdiction has evidence that the system complies with the routine inspection duty and was inspected by an authorized third-party inspector.
Source: WAC 246-272A-0270, read 2026-09-18.
A lot of Pierce County is on the annual cycle without knowing it
The three-year cycle applies only to the simplest system there is. Pierce County has an unusually large population of everything else, because so much of the county sits on ground that will not take a conventional gravity drainfield. Dense glacial till across the Gig Harbor peninsula, University Place and the Bonney Lake plateau pushes designs toward mounds and pressure systems. The Puyallup, Carbon and White river valleys have a shallow water table in lahar sediment, which does the same thing.
The practical consequence is a large number of owners who believe they are on a three-year cycle and are actually a year or more overdue. That gap becomes visible when the property sells, because a buyer on an alternative system will ask for the maintenance history.
Questions about inspection requirements
How often does Washington require a septic inspection?
At least once every three years for a system that is only a sewage tank and a gravity subsurface soil absorption system. Annually for every other on-site sewage system type. That is WAC 246-272A-0270.
Who is allowed to perform it?
A maintenance service provider authorized by the local health officer, which WAC 246-272A-0010 defines as a management entity certified by the local health officer. The rule makes no provision for an owner inspecting their own system. Pierce County publishes a list of certified companies, and the Health Department is the authority on who qualifies here.
What happens if I have missed inspections?
Get current. There is no way to retroactively create a record for years that were not inspected, and a gap is a question a buyer will ask about. The practical step is to book an inspection now and start building the record forward.
Does the sale inspection replace the routine one?
They serve different purposes. Pierce County's Report of System Status supports a property transfer; the routine inspection is the ongoing obligation on the owner regardless of whether the property is selling. Ask the Health Department how a recent inspection interacts with your cycle, because under state rule an inspection by an authorized third-party inspector can bear on whether a transfer inspection is required.
Get a free inspection quote
Your request goes straight to an on-site sewage professional certified by the Tacoma-Pierce County Health Department and serving Pierce County, usually within about an hour during the day, not a national lead list.
Prefer to talk? Call (253) 367-7679.