Damp and moisture meters
Does a damp streak that tracks a radiator pipe point to the plumbing rather than the damp-proof course?
Yes, a wet line that follows a radiator pipe is a plumbing clue: a weeping joint, a pinhole or condensation on a cold pipe can track that route. It is not the pattern of rising damp. The survey can record the line, but it does not pressure-test the heating.
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?
Heating pipes often run at skirting level or drop beside a radiator. If the damp, the blistered paint or the salt follows that pipe and stops where the pipe stops, the pipe is the suspect. Rising damp is looked for as a broader band tied to the base of the wall and to outside levels, not as a stripe under one fitting. A valve leak is one version of this. A long run that weeps at a joint is another. The survey describes the stripe it could see.
Services in a home survey are looked at visually. They are not safety-tested and the heating is not pressure-tested. A system that was off, or drained, may hide a weep until it is refilled. Do not rename the stripe as a failed damp-proof course in a message to the seller. Ask a plumber to look at that pipe if the rating matters before you commit. The survey will not have tightened the joint.
What should you ask your surveyor?
- Does the damp follow the pipe, or does it run the length of the wall?
- Was the heating on, off, or apparently drained?
- Are you sending this to a plumber rather than a damp-proofing firm?
What are the typical next steps?
- Do not inject the wall along a line that matches a pipe.
- Ask the seller when the heating last ran. A dry joint on the day may still weep.
- Keep any plumber's visit to the pipe the survey 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
Can a cold pipe sweat and look like a leak?
Yes. Condensation on an uninsulated cold pipe can wet the same route. The survey may not be able to say which, if the pipe was dry at the visit.
Does lagging prove there is no leak?
No. Lagging can hide a weep. It can also be the right finish on a pipe that only sweats.