What should you ask if the house is not on a mains sewer?

What is the fuller explanation?

Off-mains drainage can be a septic tank, a treatment plant or a cesspool. Each has different duties under the English guidance, and other nations differ. Shared systems make you jointly responsible if the official page’s definition of operator applies. Get the share in writing: a handshake with a neighbour is thin evidence.

The home survey will not map the drainage field or prove the ground can soak water away. A wet, smelly garden can be a failed field. It can also be a spring. Ask a drainage specialist if the survey has raised it. Their investigation has a cost. Ask what tests they will do, such as a percolation test, before you agree.

What should you ask your surveyor?

• What covers, vents or outfalls did you see?
• Was any chamber too dangerous or too stuck to open?
• Do you suspect a failed drainage field, or are you only noting private drainage?

What are the typical next steps?

1. Put the off-mains questions in the solicitor’s list this week, not after exchange.
2. Identify the system before you negotiate a replacement price.
3. If it is shared, meet the fact with the neighbour through the solicitor, not through a row at the gate.

Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.

Also asked about this

Which pages should you read next?

• Does a home survey prove the drainage field meets the general binding rules?
• What changes for septic tanks in Scotland, Wales or Northern Ireland?
• Can a leaking drain under a bay mimic subsidence cracks?
• Guide: What do drainage defects mean in a home survey?
• All UK home survey questions

Sources

• GOV.UK: Septic tanks and sewage treatment plants: what you need to do
• GOV.UK: General binding rules for small sewage discharges, in force from 2 October 2023 (England)