Septic inspections in King & Snohomish County

/ Septic inspections, explained

A septic inspection is the clearest way to know what is really happening underground. It tells you whether your system is working the way it should, catches small problems before they become expensive ones, and keeps you in good standing with the county health department. In King County and Snohomish County, inspections are not optional extras. Both counties require septic owners to have their systems inspected on a regular schedule, and both now require an inspection when a home is sold.

Septic Response inspects septic systems for homeowners, buyers, sellers, real estate agents and property managers across all of King County and every city in Snohomish County. Our technicians are WOSSA-certified and certified on-site system maintainers in King County. We inspect gravity systems and every common alternative system in the region, explain what we find in plain English, and file inspection reports within 24 hours so closings and county deadlines stay on track.

Why septic inspections matter

A septic system can look perfectly fine from the yard while a problem develops below the surface. A cracked baffle lets solids escape toward the drainfield. A float sticks and a pump stops dosing. Roots work their way into a line. An effluent filter slowly clogs until water backs up into the house. None of these announce themselves until the damage is done.

A good inspection finds these issues early, when the fix is usually a part or an adjustment instead of a new drainfield. It also creates a record. Every inspection report on file with the county builds a history of your system that protects you when you sell, helps the next technician understand your system faster, and shows that you have met your responsibilities as an owner. Washington State law makes owners responsible for inspecting and maintaining their septic systems, and the counties enforce that responsibility.

How often your system must be inspected

How often you need an inspection depends on the type of system you have and the county you live in.

• Conventional gravity systems: every three years in both King County and Snohomish County.
• Alternative systems such as pressure distribution, mound, sand filter, aerobic treatment unit and drip systems: more often. Snohomish County inspects alternative systems annually unless the manufacturer requires more frequent service. Public Health – Seattle & King County lists shorter intervals for these systems as well, and some manufacturers require more.
• Systems serving food service businesses in King County: at least yearly.

If you are not sure what type of system you have, your as-built drawing will tell you. You can look it up through King County’s septic records or the Snohomish County Health Department. Or call us. We will figure out your system type and your schedule with you. After every inspection we tell you when the next one is due, and our maintenance and monitoring page explains how ongoing service works for advanced systems.

What a septic inspection includes

Every system is different, so every inspection is tailored to the components you actually have. A thorough inspection typically covers:

• Locating and accessing the system. We find the tank and other components and open the lids. Risers make this much faster.
• Tank levels. We measure sludge and scum to see whether pumping is needed now or when it will be.
• Baffles, tees and the effluent filter. These keep solids in the tank. We check that they are in place, intact and not clogged.
• Inlet and outlet lines. We look for blockages, backups and signs of root intrusion or settling.
• Tank condition. We look for cracks, leaks and groundwater getting in, which can overload a system.
• Pumps, floats, alarms and control panels on pump, pressure and advanced systems. We confirm the pump runs, the floats switch correctly and the alarm sounds when it should.
• Treatment units and filters on ATUs and sand filter systems, following the manufacturer’s checklist.
• The drainfield area. We walk the field for surfacing effluent, soggy ground, odors and damage from vehicles, roots or construction.
• Lids and safety. We check that lids are intact and secured. King County’s updated code, in effect since April 2025, requires secured tank lids.

If a component cannot be located or evaluated, we note it on the report, as the counties require. If something needs repair, we explain what we found, why it matters and what your options are, and we tell you what can safely wait.

Home sale inspections in King County

In King County, a septic system must be inspected by a certified on-site system maintainer before the title of a property transfers. The inspection report goes to Public Health – Seattle & King County, which typically reviews reports within ten business days, and the reports can be viewed through the county’s OnlineRME system.

Some sales qualify for a waiver of the separate time-of-sale inspection, for example when a full operation and maintenance report has been filed within the past six months, when the owner has been filing reports regularly, when the home is new construction that has never been occupied, when a new system’s first inspection is not yet due, or when the system has been abandoned because the home is connected to sewer. If you are not sure whether your sale qualifies, ask us before you list. Because we file inspection reports within 24 hours, our inspections fit comfortably into most closing timelines.

Home sale inspections in Snohomish County (new November 2026)

Starting November 1, 2026, anyone selling a property with a septic system in Snohomish County must complete the Health Department’s property transfer requirements before closing. Sellers need:

1. A full inspection by a certified septic contractor within the past 12 months, plus pumping if the inspection report recommends it.
2. An as-built on file with the Health Department. If there is none, a certified septic contractor completes an On-Site Sewage System Site Plan instead.
3. A Report of Property Transfer application and fee, submitted through the Health Department’s online portal.

The Health Department reviews the application and records and returns the report with or without deficiencies noted. Surfacing sewage and immediate health or safety hazards, including unsecured or makeshift tank lids, can trigger a site visit and enforcement. The rule applies to homes, duplexes and commercial properties alike. Systems installed within the past 12 months are exempt. Our step-by-step guide, selling a home on septic in Snohomish County, walks through the whole process.

Advice for buyers

If you are buying a home on septic, the inspection report is one of the most important documents in your file. Read the findings carefully, ask what any deficiency means in practical terms, and find out when the next pumping and inspection are due. In Snohomish County, unresolved surfacing sewage or hazards become the new owner’s responsibility after closing. If you are new to septic, our new homeowner septic guide explains what to do in your first few months, and we are always happy to walk new owners through their system.

Advice for sellers and agents

• Start early. Book the inspection four to six weeks before listing so there is time for pumping, a site plan or repairs without delaying closing.
• Check your records. Recent maintenance reports can save time and, in King County, may qualify the sale for a waiver.
• Fix easy items first. Loose or cracked lids are simple to fix and are one of the few items that can trigger enforcement.
• Use rebates. In Snohomish County, Savvy Septic rebates still apply to inspections, pumping, risers and minor repairs done for a sale, for residential properties whose owners complete the free online Septic Care Workshop.

Routine maintenance inspections for advanced systems

Pressure distribution, mound, sand filter, drip and aerobic treatment systems work well when they are maintained, and they are required to be inspected more often than gravity systems for good reason. They depend on pumps, timers, floats, alarms and treatment components that wear over time. A routine inspection keeps those parts working and keeps your county filings current. We service Oscar and Bio-Microbics aerobic units and the other system types common in western Washington. See ATU service and maintenance and monitoring.

Common problems we find during inspections

Most inspections end with good news or a short list of small fixes. When we do find something, it is usually one of these:

• A tank overdue for pumping. The most common finding by far. Solids are close to the outlet, and pumping now protects the drainfield from damage.
• Missing or damaged baffles. Concrete baffles can deteriorate over decades. Without them, solids and scum flow straight toward the drainfield. A replacement outlet tee or baffle is a modest repair that protects a very expensive part of the system.
• A clogged effluent filter. Filters do their job by catching solids, so they need cleaning. A badly clogged filter can back water up into the house.
• Pump, float or alarm problems. On pump systems, floats can tangle or stick, alarms can be silenced or disconnected, and pumps wear out. Each can let a pump chamber overflow or stop the drainfield from being dosed properly.
• Groundwater or rainwater getting in. Cracked tanks, loose risers and poorly sealed lids let water in during our wet winters, which overloads the system and can flood the drainfield.
• Roots and settling. Tree roots find small gaps in pipes and lids. Settled pipes can create low spots where waste collects.
• Drainfield stress. Soggy ground, surfacing effluent or damage from vehicles, livestock, irrigation or construction over the field.
• Unsafe lids. Cracked lids or makeshift covers such as plywood, pallets or sheet metal. These are a real safety hazard and one of the items that can trigger county enforcement during a Snohomish County sale.

The earlier these are caught, the smaller the fix. That is the whole point of a regular inspection schedule.

How to prepare for your inspection

• Gather what you have. Your as-built drawing, past pumping and inspection reports, and any repair records help us work faster and give you a better picture of your system’s history.
• Clear access. Move anything sitting over the tank lids or the pump chamber and unlock gates.
• Use water normally. We want to see the system working under everyday conditions, so there is no need to stop using water before we arrive.
• Tell us about symptoms. Alarms, odors, slow drains or wet spots, even ones that went away, help us look in the right places.
• Keep the drainfield clear. Keep cars and heavy equipment off it, before and after the inspection.

Understanding your inspection report

Your report records what type of system you have, the condition of each component we inspected, tank levels, any components we could not locate or evaluate, and any deficiencies and recommendations. We file it with the county health department, where it becomes part of your property’s permanent septic record. If a finding is unclear, ask us. We would rather spend a few extra minutes explaining than have you guess what a line on a form means. A clean report is also a valuable selling point, because buyers and lenders increasingly ask for it.

Inspection or pumping: which do you need?

They are different services, and many visits include both. Pumping removes the sludge and scum from the tank. An inspection evaluates the whole system and is what the counties require on a schedule. If your inspection shows the tank needs pumping, we can usually pump on the same visit. Learn more about septic tank pumping.

What happens after the inspection

We walk you through the findings, in person when you are home or by phone when you are not, and file the inspection report within 24 hours. If everything checks out, you will know when the next inspection is due. If something needs attention, you will get a clear explanation of what is wrong, what it affects and the options to fix it, from simple adjustments to septic repairs or drainfield repair. We never pressure customers into work they do not need, and we will always tell you what can safely wait.

Why choose Septic Response for your inspection

An inspection is only as good as the person doing it and the honesty of the report. Our technicians are trained to diagnose the full range of systems found in western Washington, not just to run a pump truck. We are WOSSA-certified, certified on-site system maintainers in King County, and licensed, bonded and insured. We know both counties’ rules, including Snohomish County’s brand-new property transfer program, and we file reports within 24 hours. Most of all, we explain what we find plainly, so you can make good decisions about your home.