Short definition
A cesspool (or cesspit) is a sealed underground tank that receives household sewage with no outlet. It must be pumped out periodically. Modern Washington heavily restricts cesspools — they’re permitted only as an interim measure or in narrow circumstances. Old residential cesspools (pre-1960 in WA) are increasingly being decommissioned and replaced with modern septic systems during property transfer.
What it is
The simplest possible on-site sewage option: a buried tank with one inlet and no outlet. Sewage accumulates and must be pumped out before the tank fills. The setup was common in pre-1960 rural Washington when neither public sewer nor a soil-suitable drainfield was available, and on small lots where there was no room for a proper septic system.
The structural problem is also the regulatory one: with no outlet, a cesspool is entirely a holding container. Once it fills, it overflows or seeps through the walls into the surrounding soil. Aging concrete or steel walls crack and contaminate groundwater. WA’s adopted on-site sewage rule (WAC 246-272A) treats cesspools and holding tanks under restrictive conditions; county health departments require maintenance contracts and frequent pumping for any approved holding tank, and replacement with a modern septic system is the typical remedy when cesspools are discovered during property transfer.
Why it matters to a homeowner
If you’re buying older rural Washington property and the pre-purchase inspection finds an old cesspool, you’re likely looking at decommissioning and replacement with a modern septic system before closing — or as a near-term obligation after purchase. Decommissioning typically means draining the tank, then either filling with sand/gravel or crushing the concrete walls and backfilling, certified by the county health department.
Common variants / not the same as
- Cesspool vs. septic tank. Cesspool has no outlet. Septic tank has an outlet to a drainfield.
- Cesspool vs. holding tank. In modern US usage, “holding tank” is the legal/permitted version of the same concept under specific approvals.
- Cesspool vs. pit privy. Pit privy is a solid-waste-only outhouse. Cesspool receives full household sewage.
- Cesspool vs. drywell or soakaway. A drywell infiltrates rainwater into soil. A cesspool seals.
Common failure modes
- Capacity exceeded → backup into the home.
- Aging concrete or steel walls cracking → groundwater contamination.
- Lid corrosion → cave-in and collapse risk.
- Owner deferring pump-out → environmental violation in WA.