Basements and cellars
The cellar sump has a pump and no second pump was seen. What happens to that system in a power cut was not tested?
What happens to that sump in a power cut was not tested. The survey saw one pump and did not see a second. It has not switched the supply off, has not run a battery, and has not proved an alarm. A pump that needs mains power stops when the power stops, and water that would have been lifted can then rise in the chamber. The survey has not shown that this pump is wired that way, and it has not shown a backup either. The system with the power off remains untested.
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 cellar sump collects water at a low point and a pump lifts it away. If there is only one pump and it depends on the mains, a power cut during wet weather is a failure of the only machine. A second pump, a battery or another supply would be a different arrangement, and none of those was seen or tested. The survey can describe the chamber it saw. It cannot say how high water would stand, or how quickly, with the pump dead. That trial was not done.
Tell the solicitor a single sump pump was seen and that behaviour in a power cut was not tested. If the cellar stays dry only because of the pump, ask a drainage firm, separately, what backup exists. The home survey has not camera-surveyed the pump line and has not run the power-off trial. Do not describe the cellar as protected because a pump was present. Presence in the chamber is not a test of the system with the supply off.
What should you ask your surveyor?
- Was only one sump pump seen, with no second pump in view?
- Did you leave behaviour in a power cut untested?
- What of the pump chamber did you actually see?
What are the typical next steps?
- Treat power-cut performance of the sump as untested.
- Tell the solicitor only one pump was seen.
- Ask a drainage firm about backup if the cellar relies on the pump.
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
If the pump runs during the visit, is the cellar covered in a power cut?
No. A pump running on the mains during a visit shows it can run then. It does not show what happens when the power stops, and no second pump was seen. The survey did not carry out that test. An hour of ordinary running is not a backup for the sump.
Does a high-level alarm take the place of a second pump?
Only if an alarm is fitted and was tested. The survey saw neither a second pump nor a tested alarm. An alarm, even if added later, warns someone. It does not lift the water. The survey has not assessed an alarm and has not tested a power cut.