Electrics and gas
There is a magnetic filter on the heating return. Does that mean the system was serviced?
No. A filter on the heating return is only a pot on the pipe, usually near the boiler, and seeing it is not a service record, a power flush or a gas safety check. The survey did not open the magnet or test the boiler. If the heat source is gas, HSE expects a Gas Safe registered engineer to do that gas work.
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?
Filters catch sludge. They are fitted on many modernised systems and on many that are still dirty. The surveyor can say the pot is there, that it is leaking, or that the valves look seized. They cannot say when it was last cleaned. A label with a date is the installer’s or the engineer’s mark, if you can read it, not a test the surveyor repeated. Do not unscrew the magnet on a viewing. The water is hot and black, and opening it is not the inspection you paid for.
Ask the seller for service invoices if you want a history. An owner-occupier does not have to hold a landlord gas safety record for the sale. A Gas Safe visit, if you book one, looks at the gas appliance. Cleaning a filter may be part of a heating service they agree to do. It is not automatic, and it is not evidence that the radiators are clear. Keep the filter sentence smaller than the boiler sentence. One brass pot does not pass the flue, the ventilation, or the controls.
What should you ask your surveyor?
- Did you see a filter, and did you see a leak at it?
- Was any service record shown to you, or only the pot?
- Did you open it? Please say if you did not.
What are the typical next steps?
- Do not open the filter.
- Ask the seller when it was last cleaned, and treat the answer as theirs, not as a test.
- If the boiler needs a safety check, book a Gas Safe engineer. The filter does not replace that.
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
Does a missing filter mean the heating has failed?
No. Many systems have none. Absence is not a leak and not a sludge measurement.
Is the filter an electrical device the survey tested?
No. It is pipework. The survey did not test the electrics either.