Most people shopping for rural property along the Highway 2 corridor have at least a general understanding of septic systems. They know the home isn't on city sewer, they know there's a tank and a drainfield somewhere in the yard, and they know it needs to be maintained. But cesspools are a different story — and they're one of those things that can catch buyers and sellers off guard if nobody's paying close attention.
I bring this up because it comes up. Not every week, but often enough that it's worth talking about. Some of the older homes between Monroe and Skykomish were built decades ago, well before modern onsite wastewater standards existed, and a handful of them still have cesspools rather than proper septic systems. If you're buying or selling a property out here, it's worth understanding what that means and why it matters.
What a Cesspool Actually Is
A cesspool is essentially a hole in the ground — typically a buried pit or a bottomless tank, sometimes lined with brick or stone — where household wastewater goes. There's no real treatment happening. Sewage flows into the pit, and liquid seeps out through the walls or the open bottom into the surrounding soil. Solids accumulate at the bottom over time and eventually need to be pumped out, though in practice that didn't always happen regularly.
The key difference between a cesspool and a modern septic system is treatment. A properly designed septic system uses a sealed tank to separate solids from liquids and then distributes the liquid effluent through a drainfield, where aerobic bacteria in the soil do the critical work of actually treating the wastewater before it reaches the groundwater. A cesspool skips most of that process. Untreated wastewater goes straight into the ground, often at depths where the oxygen-dependent bacteria that provide final treatment simply aren't present.
Cesspools were common in rural areas for a long time because they were cheap and easy to install, and when population density was low and lots were large, the environmental impact wasn't always obvious. But as we've learned more about groundwater contamination and public health, the standards have changed — and for good reason.
How Washington State Views Cesspools
The Washington State Department of Health is straightforward about this: a cesspool — untreated wastewater going directly into a bottomless tank — may meet the definition of a failing onsite sewage system. The same goes for seepage pits, which are similar in concept. When a system is classified as failing, the expectation is that it gets abandoned and replaced with a system that actually treats wastewater to modern standards.
This isn't a gray area or a technicality. The state's position is grounded in the reality that cesspools can contaminate groundwater and surface water, which is a serious concern along a corridor like ours where many homes also rely on private wells for drinking water. If your wastewater system isn't treating what goes into the ground, and your neighbor's well is drawing from that same ground, the implications are pretty clear.
Snohomish County enforces these standards through the Snohomish County Health Department, which oversees all onsite sewage system permitting, installation, and maintenance in unincorporated areas — including the Highway 2 communities. They maintain an online database called OnlineRME where you can look up as-built drawings and records for a property's septic system using the parcel number or address. That's a useful first step if you're trying to figure out what kind of system a property has before you get too far into a transaction.
What This Means for Buyers
If you're looking at an older home along the corridor — and by older I mean anything built before the mid-1970s or so, though it varies — it's worth asking early in the process what kind of wastewater system the property has. A standard home inspection won't necessarily catch this. You'll want a septic-specific inspection by a licensed professional who can evaluate the system type, condition, and whether it meets current standards.
If the inspection reveals a cesspool or a seepage pit, you're looking at a property that will almost certainly need a new septic system. That's not a small expense. A conventional gravity-fed septic system in our area typically runs somewhere in the range of $5,000 to $12,000 or more depending on the property's soil conditions, terrain, and how much site preparation is needed. If soil conditions are poor or the water table is high — both of which are common in parts of the Skykomish River valley — you may need an alternative or mound system, which can push costs well above $15,000. Add in percolation testing, design work, permits, and decommissioning the old cesspool, and the total can add up quickly.
None of this means you should walk away from a property with a cesspool. It means you should know about it before you make an offer, factor the replacement cost into your budget, and potentially negotiate accordingly. This is exactly the kind of due diligence that matters when you're buying rural property, and it's one of the reasons I always encourage buyers to look beyond the surface-level listing details.
What This Means for Sellers
If you're selling a property that has a cesspool, the most important thing is disclosure. Washington's seller disclosure form asks about the type of sewage system on the property, and answering that question accurately is both a legal obligation and the right thing to do. Surprises during the inspection process rarely work in a seller's favor.
Some sellers choose to replace the cesspool with a modern septic system before listing, which can simplify the transaction and remove a potential negotiating issue. Others disclose the situation and price the home with the understanding that the buyer will handle the upgrade. Either approach can work — the key is being upfront about it.
It's also worth noting that Snohomish County currently does not require a property transfer inspection for septic systems, unlike King County, which has specific time-of-sale inspection requirements. That said, most buyers and their lenders are going to want an inspection regardless, and if that inspection reveals a cesspool, it's going to come up. Better to address it proactively than to have it derail a deal late in the process.
Decommissioning a Cesspool
When a cesspool is replaced, it can't just be left in the ground. Washington State rules require that anyone permanently abandoning a septic tank, cesspool, or seepage pit follow specific decommissioning procedures, which generally involve pumping the tank, crushing or removing it, and filling the void. This is a safety issue as much as an environmental one — an old, deteriorating cesspool can be a collapse hazard. The Snohomish County Health Department should be notified when a system is decommissioned so they can update their records.
The Bigger Picture
Cesspools are becoming rarer along the corridor as older properties change hands and systems get upgraded. That's a good thing for the overall water quality of the area, especially in communities that sit close to the Skykomish River and its tributaries. Snohomish County offers resources through its Savvy Septic Program, including free workshops, rebates for inspections and maintenance, and financial assistance for major repairs. If you're a homeowner with a system that's aging or uncertain, those programs are worth looking into.
For anyone buying or selling rural property along Highway 2, the takeaway is simple: know what's in the ground. Whether it's a cesspool, a gravity system, a pressure distribution setup, or something else entirely, understanding the wastewater system on a property is one of the most important pieces of due diligence you can do in rural real estate. It's not the most glamorous topic, but it's one that can save you significant money and headaches down the road.
If you have questions about a specific property or want to talk through what to look for in a cesspool situation, feel free to reach out at josh@highway2realestate.com. I'm always happy to help you think through the details.
Josh White is a licensed real estate broker with Horizon Real Estate, specializing in homes, land, and rural properties along the Highway 2 corridor in Washington State.