Electrics and gas
A combi boiler has no service sticker and the heating was on. What has running the heating not proved about the flue or the heat exchanger?
Running the heating has not proved the flue or the heat exchanger. The combi was on, so the survey knows the system produced heat during the visit. It does not know the condition of the flue, the combustion, or the heat exchanger inside the boiler. There is no service sticker. A home survey is not a gas safety inspection and not a boiler service. Heat at a radiator is an operation check of the most basic kind. It is not a strip-down and not a flue analysis.
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?
Combis hide the parts that fail quietly. The heat exchanger is inside the case. The flue is a route for exhaust that a warm room does not certify. A service sticker, had there been one, would only have been a label that someone attended, and even that label is absent. The surveyor may note noises, leaks at valves, or a terminal they could see from outside. Those notes are still not a service. Switching the heating on does not open the case and does not sample the flue gases.
Ask the seller, through the solicitor, for service history on this combi, and do not treat silence as a clean boiler. If you need a current view of the flue and the heat exchanger, that is a Gas Safe registered engineer, not a reread of the survey. Tell them there was no sticker and that the heating happened to be running. Keep the survey honest: it recorded an unstickered combi that was on, and it left the flue and the exchanger unproved.
What should you ask your surveyor?
- Did the heating run, and did you open the boiler or analyse the flue?
- Was any service sticker present on this combi?
- What have you deliberately not claimed about the heat exchanger?
What are the typical next steps?
- Treat a running heating system as heat on the day, not a service.
- Do not read the missing sticker as a pass for the flue or the exchanger.
- Ask for service history and a Gas Safe check if you need those parts assessed.
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 radiators get hot upstairs, has the heat exchanger been proved?
No. Hot radiators show that water was heated and moved. They do not show the internal condition of the exchanger or the flue. The survey has not proved either, and there was no service sticker. Heat at a radiator is not a service.
Does a new programmer on the wall count as a boiler service?
No. A programmer is a control. It does not service the combi, inspect the flue, or replace the sticker that was not there. The heating running still leaves those parts unproved. Controls do not open the case or the flue.