Electrics and gas
The boiler condensate is pumped uphill to a sink. Why is a failed pump not a roof leak?
Because the water comes from the boiler’s condensate, lifted by a small pump to a waste, and if the pump stops the water appears in or under the boiler cupboard rather than from the roof. The survey did not test the pump or service the boiler. Gas work is for a Gas Safe registered engineer.
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?
Many combis and other boilers produce condensate that must be discharged. A pump is used when the waste is higher than the boiler, including a sink upstairs or a stack the gravity pipe cannot reach. The surveyor can see the pump, the slim pipe rising, and any staining in the cupboard. They cannot say the non-return valve holds, and they do not run the pump as a formal test. A ceiling stain near a rising pipe may be this water. It may also be a pipe joint or, somewhere else, a roof. The location has to be described. Do not file every stain as tiles.
A failed pump can stop the boiler, because many appliances will not run if condensate cannot leave. That is a heating fault, still not a roof defect. HSE expects gas appliance work to be done by a Gas Safe registered engineer. Replacing a pump may be part of what they, or a heating engineer, quote. The survey has not priced it and has not declared the flue safe because the pump looks new. Owner-occupiers selling are not under a landlord’s gas-record duty. Ask for service papers, and point the engineer at the pump if you book them. Do not confuse this uphill pipe with a condensate pipe that only drips outside and might freeze. This one is a pump to a sink.
What should you ask your surveyor?
- Did you see a pump and a pipe rising to a waste, or only a stain?
- Did you test the pump?
- Are you keeping this distinct from a roof leak?
What are the typical next steps?
- Do not pour water into the pump and call it tested.
- If the cupboard is stained, tell a heating engineer or a Gas Safe engineer where.
- Do not instruct a roofer for a stain that the survey has tied to this pump, unless a separate roof defect is described.
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 sink gurgles, has the pump passed?
No. A noise is not a test of the pump or of the boiler.
Is condensate the same water as a leaking radiator?
No. It is from the boiler. A radiator leak is a different pipe. The survey should say which stain it means.