SurveySorted
Menu
Sign in

Drainage and septic tanks

What should you ask for if a house has a septic tank the survey could not open?

Ask the seller for emptying records and where the effluent goes, and treat the tank as not inspected. GOV.UK describes a septic tank as treating sewage and releasing liquid. In England, the general binding rules from 2 October 2023 set volume limits and require an infiltration system for a discharge to ground, and a treatment plant for a discharge to surface water. The survey has not measured the volume and has not proved the outfall.

Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.

What is the fuller explanation?

A cover in the garden is not a test. The operator, which can be you once you own it, or jointly if it is shared, is responsible under the GOV.UK guidance. Wales, Scotland and Northern Ireland have different rules. Do not apply the English binding rules to a Welsh hillside without checking.

Emptying invoices show use. They do not show that a drainage field exists. If you need that known, instruct someone who will find the outfall. There is no RICS price for that search. Do not deduct a new treatment plant until you know this one discharges unlawfully.

What should you ask your surveyor?

  • Could you open the tank?
  • Did you see a ditch outfall or only a cover?
  • Are you applying English rules to a house outside England?

What are the typical next steps?

  1. Get the invoices and any consent or registration the seller holds.
  2. Walk the ground for a discharge only if it is safe and you have permission.
  3. Ask a drainage firm, not the surveying firm, to confirm the outfall if the purchase depends on it.

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

Is a cesspool allowed to discharge?

A cesspool stores sewage for removal. It is not the septic tank GOV.UK describes as treating and releasing liquid. The survey may not be able to tell them apart from a cover.

Does a shared tank split the bill by the survey?

No. Sharing is a legal and practical arrangement. GOV.UK says shared users can be jointly responsible. The survey does not apportion the invoice.

Sources