How each system works
| Septic tank | Cesspit | |
|---|---|---|
| Treatment | Settles solids, treats liquid, disperses it into the ground via a drainage field | None — stores everything until it is pumped out |
| Emptying frequency | At least once a year in England, or to manufacturer instructions; 12–24 months in Wales | Far more often — often every 4–8 weeks depending on size and occupancy |
| Typical emptying cost | £175–£313 typical, average about £225 | £175–£300 per visit |
| Typical annual cost | One or two empties — roughly £175–£625 a year | Seven to thirteen empties — often £1,000+ a year |
Both need the same kind of tanker visit; the difference is how many visits a year you pay for.
Emptying frequency
A septic tank runs for months between empties because most of the volume leaves as liquid through the drainage field. A cesspit holds everything that goes down the drains — bathwater, washing machine water, everything — so it fills on a timescale of weeks, not months. Real cesspit intervals vary with tank size and occupancy: often every 4 to 8 weeks, sometimes longer. There is no universal interval, so ask your carrier what your tank implies.
Annual cost: ranges, not fake precision
Put the numbers together as a thought experiment. A cesspit at £175–£300 per visit (MyJobQuote’s range), emptied every 4–8 weeks, means roughly 7–13 visits a year — in the order of £1,225–£3,900 annually. A septic tank at £175–£313 per typical empty (Checkatrade 2026), emptied once or twice a year, lands around £175–£625. Those are planning ranges, not quotes: your tank, your household and your carrier move them. The shape is reliable though — for the same house, a cesspit is a running cost and a septic tank is an occasional one.
For your own figures, see cesspit emptying cost or run the emptying cost calculator.
Which one do you have?
If you are not sure: a septic tank normally has an outlet into the ground and needs a drainage field somewhere nearby; a cesspit is sealed and has to be emptied far more often. The emptying history is the giveaway — if the tanker visits every few weeks, it is a cesspit. When buying a property with either system, an inspection will tell you which you are inheriting and what condition it is in.