Electrics and gas
One valve on an underfloor manifold is wet at the spindle and the loops were cold. What does that drip show, and what slab leak has it not located?
The drip shows a wet spindle on that one manifold valve, and it has not located a leak in the slab. The survey can see moisture at the spindle of the valve that was wet. The loops were cold, so the system was not seen running. No pressure test was done, and no pipe under the floor was exposed. A drip at a valve on the manifold is a leak at that valve. It is not a map of a slab leak.
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?
Underfloor loops run from the manifold into the floor. A wet spindle is on the valve you can see, at the face of the manifold. Water there can come from the gland of that valve. It does not show which loop, if any, is wet inside the slab, and cold loops mean the surveyor did not watch the system heat. The home survey did not electrically test the controls either. The finding stops at the valve that was wet.
Ask a heating engineer to inspect the wet valve and to test the loops if you need to know whether the slab is involved. Keep that separate from the home survey. Tell the solicitor the note is a drip at one spindle, not a located slab leak. Do not lift the floor on the back of this visit. Nothing under the floor was seen.
What should you ask your surveyor?
- Does the drip show the spindle of one manifold valve?
- Was any leak inside the slab left unlocated?
- Were the loops cold, so the system was not seen running?
What are the typical next steps?
- Describe the wet spindle, not a mapped slab leak.
- Ask a heating engineer to inspect that valve and the loops.
- Do not open the floor on the strength of this drip alone.
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 only one valve is wet, are the loops proved dry?
No. A dry-looking floor and cold loops do not prove the pipes in the slab. The survey saw a wet spindle. It did not pressure-test the loops or expose them. A drip at one valve has not located a slab leak anywhere under the floor.
Does a wet spindle mean the manifold electrics were tested?
No. Moisture on a valve is a plumbing observation. The home survey did not electrically test the manifold controls, the pump or the wiring. The drip has not become an electrical test. Cold loops were noted, not energised. Nothing electrical was measured at that manifold.