Electrics and gas
The programmer clicked on and several radiators stayed cold. What has that shown about the controls, and what sludge in the system was not diagnosed?
The click has shown that the programmer tried to call for heat, and it has not diagnosed sludge. Several radiators stayed cold after the control moved. That separates a dead programmer from a system that was asked to heat and did not heat those emitters. The survey did not sample the water, did not open a radiator, and did not name sludge, a stuck valve, air or a pump fault. Cold surfaces are an observation. They are not a diagnosis of what is in the pipes.
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 programmer is the time control. If it clicks to on and the boiler or the pump responds, the control has at least asked. Radiators that stay cold may be valved off, airlocked, blocked or on a circuit that did not circulate. Sludge, the magnetite debris in old systems, is one candidate among others. The survey did not drain a drop or test a valve. Feeling a cold panel does not tell those causes apart, and it does not show that the programmer itself is faulty.
Ask a heating engineer to find why those radiators stayed cold, and keep sludge as a possibility they may test, not as a finding of the survey. Tell the solicitor the report shows a control that clicked and emitters that stayed cold. Do not send the note out as a power-flush specification. The home survey did not diagnose the water and did not repair a valve.
What should you ask your surveyor?
- Which radiators stayed cold after the programmer clicked on?
- What did that show about the controls, as against the emitters?
- Did you diagnose sludge, or leave the cause of the cold radiators open?
What are the typical next steps?
- Read the click as a control that called for heat.
- Leave sludge undiagnosed until a heating engineer tests the system.
- Do not turn the cold radiators into a specified flush.
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 one radiator warmed, are the cold ones simply turned down?
They might be, and the survey has not said which. A programmer click with mixed radiator temperatures shows the call for heat reached some of the system. It does not identify closed valves, air or debris in the ones that stayed cold. No valve was dismantled and no water was sampled. The cause on each cold panel remains open.
Does a noisy boiler mean the sludge has been found?
No. Noise was not the test, and sludge was not diagnosed. The survey recorded a programmer that clicked and radiators that stayed cold. It did not inspect the water and it did not name debris as the cause. Boiler sound, if it was heard, is a separate comment and not a laboratory result on the system.