How Often Should a Boiler Be Serviced?

Every 12 months. Book it for the same month each year, late summer or early autumn if you can, so faults are found before you need the heating and the guarantee record has no gaps. Landlords have a separate legal duty for an annual gas safety check; see our guide to the landlord gas safety certificate.

Three reasons. Safety: the engineer measures combustion with a flue gas analyser, checks the flue and the seals, and confirms the boiler is not producing carbon monoxide. Reliability: worn seals, dirty electrodes, a blocked condensate trap and an expansion vessel that has lost charge are all found and dealt with before they stop the boiler on a cold morning. And the guarantee: most manufacturers require an annual service recorded in the Benchmark service record in your manual, and a gap gives them grounds to decline a claim.

Late summer and early autumn are the sensible window. Faults are found while the heating is not needed, parts are easier to get, and you are not waiting behind a queue of no-heat callouts in December. If you have just moved into a home with no paperwork, book one straight away so you have a baseline and know whether the boiler is still within its guarantee.

A service is a set of measurements, not a wipe over. The engineer runs the boiler up to temperature and analyses the flue gases, checks gas pressure and rate, opens the case to inspect the burner, heat exchanger and seals, clears the condensate trap, checks the electrodes, tests the expansion vessel charge, proves the safety devices and checks the flue outside. A magnetic filter, if fitted, is cleaned, and inhibitor strength can be tested. Our boiler servicing page sets out the full checklist.

The annual visit is also the moment to look at what sits around the boiler. A magnetic system filter should be emptied, and BS 7593 asks for inhibitor strength to be checked at each annual service. On a sealed system the cold pressure is checked, and the controls are tested so the boiler is actually told when to fire. If you have an unvented hot water cylinder, its manufacturer will usually ask for an annual inspection too, so mention it when you book.

Yes, from the first year. A new boiler's extended guarantee usually depends on registration within the manufacturer's deadline and an annual service every year of the term. Miss one and the longest guarantees, such as up to twelve years on the Worcester Greenstar 8000 Life, can be shortened or refused. Our guide to how long a boiler lasts explains why servicing is one of the biggest factors in boiler life.

Get the boiler serviced now and the record signed rather than leaving it longer, then check your guarantee terms, because manufacturers differ on how they treat a gap. An unserviced boiler is not necessarily unsafe, but a missed service is the most common reason a guarantee claim on an expensive part is turned down.