Guide
Septic tank survey when buying a house: what it checks and costs
Updated
A septic tank survey when buying a house tells you what the system is, what condition it is in and whether it meets the Environment Agency's general binding rules before you exchange. UK firms that print a price charge £250 to £350, and Homeseptic prints £500 + VAT for a formal pre-purchase report.
Why a buyer needs one
A septic tank that discharges straight into a ditch, stream or river cannot meet the general binding rules; it must be replaced or upgraded, and the owner must have plans to do the work within a reasonable timescale, usually 12 months (gov.uk, discharges to surface water). The same page says buyer and seller should agree who is responsible for that work as a condition of sale. A standard building survey does not answer it, which is why the drainage is surveyed on its own.
What the survey checks
- What the system is: a septic tank, a sewage treatment plant or a cesspit.
- Where it discharges: to a drainage field in the ground, or to surface water.
- Its condition, often with the tank emptied so it can be seen.
- Whether it was built to the British Standard in place when it was installed; BS EN 12566 for new tanks and plants and BS 6297:2007 for drainage fields (gov.uk).
- How much it discharges: up to 2 cubic metres a day to ground and 5 cubic metres a day to surface water for a discharge that started before 2015 and has not changed.
What it costs
| Firm | Published price | What it is |
|---|---|---|
| Homeseptic | £250 | a visit and a verbal opinion |
| ClearFlow Surveys | from about £300 + VAT | a professional septic tank survey |
| Fastfix Drainage | from £350 | a standard domestic property survey |
| Homeseptic | £500 + VAT | a formal pre-purchase report |
Source: UK Septic Tank Survey Price Index: every row, with its source
England's rules, read on gov.uk on 27 October 2026. In Scotland a septic tank is registered with SEPA under the Controlled Activities Regulations; in Northern Ireland with NIEA.