Cesspits
Cesspit Installation
When a cesspit is the right choice, what installation involves, and what it typically costs.
In short: a cesspit is a sealed, watertight tank that stores wastewater without treating it, for later removal by tanker. It’s usually chosen when ground conditions or a lack of space rule out a septic tank or treatment plant — not as a first-choice option, given the ongoing emptying costs involved.
When a cesspit is the right choice
- Ground conditions won’t support a drainage field, and space is too limited for a treatment plant
- Very low or occasional occupancy, where infrequent emptying is manageable (e.g. some holiday accommodation)
- As a temporary solution while a longer-term system is arranged
- Sites where environmental sensitivity rules out any discharge at all
For most permanently occupied homes, a septic tank or treatment plant is usually more cost-effective long-term — see cesspit vs septic tank for a fuller comparison.
What installation involves
- Site assessment — access, expected occupancy, and tanker access for future emptying.
- Sizing — cesspits must meet a legal minimum capacity (typically 18,000 litres for a standard domestic property in England), sized up for higher occupancy.
- Installation — a sealed, watertight tank, fully buried, with no outlet — everything that goes in stays in until emptied.
- Building control sign-off — confirming the tank meets required standards for capacity and watertightness.
The ongoing cost to budget for
Unlike a septic tank or treatment plant, a cesspit doesn’t treat anything — it simply fills up, and a typical household cesspit needs emptying every few weeks. This makes the ongoing running cost significantly higher than other system types, which is worth weighing against the lower upfront simplicity. See our cesspit cost guide for more detail.
Access matters more than usual
Because a cesspit needs regular tanker emptying, access for a tanker vehicle is a genuine design constraint — worth confirming as part of the site assessment before committing to a location.
Is a cesspit the same as a septic tank? + −
No — a septic tank settles solids and relies on a drainage field to finish treating the liquid, while a cesspit simply stores everything with no treatment at all, requiring much more frequent emptying.
What's the minimum legal size for a cesspit? + −
In England, the minimum capacity is generally 18,000 litres for a standard domestic property, sized up for higher occupancy — a specialist will confirm the exact requirement for your property.
How often does a cesspit need emptying? + −
Typically every few weeks for a permanently occupied household, though this varies with occupancy and tank size — much more frequently than a septic tank.
Sources
- British Water — Code of Practice: Septic tanks and treatment plants