Boiler service and repair — what UK homeowners should know

A boiler is one of those things most people only think about when it stops working, but a little background — what the Gas Safe Register actually is, what a service does and does not cover, and what landlords are legally required to arrange — makes it much easier to spot a problem early and to know who you are allowed to let near your gas appliances in the first place.

The Gas Safe Register is the official body for gas engineers in the UK, the Isle of Man and Guernsey, operating on behalf of the Health and Safety Executive. It replaced the old CORGI scheme in 2009, and registration is not optional or a marketing badge — under the Gas Safety (Installation and Use) Regulations 1998, it is a criminal offence for anyone who is not Gas Safe registered to carry out gas work, whether that is installing, servicing or repairing a boiler, gas fire, or cooker. Working with an unregistered person is not just a risk to the quality of the work; badly installed or maintained gas appliances can leak carbon monoxide, a gas with no smell or colour that can be fatal. Before any gas work starts, it is worth asking to see the engineer's Gas Safe ID card, which lists exactly which categories of gas work they are qualified for, and checking their registration on the Gas Safe Register's own website if you have any doubt.

Most manufacturers and heating engineers recommend an annual boiler service, and it is often a condition of keeping the manufacturer's warranty valid, which is worth checking in your boiler's paperwork. A service typically involves the engineer checking the boiler's components, gas pressure, flue and safety devices, and confirming it is running safely and efficiently — it is not the same as a repair, and any faults found during a service are normally quoted and fixed separately. Costs commonly sit somewhere around £80 to £150, with many homeowners paying somewhere in the region of £100 to £120, though this varies by location and by whether you book a national provider or a local independent engineer — local independents often average a bit less. We cover typical costs for the wider range of plumbing and heating jobs, including boiler repairs, in our separate guide to what a plumber costs in the UK.

Between services, a handful of warning signs are worth acting on rather than waiting out. A yellow or orange flame instead of a crisp blue one, sooty marks around the boiler, unusual banging or "kettling" noises — often caused by limescale or sludge building up around the heat exchanger — a boiler that keeps losing pressure, or one that cuts out repeatedly, all point to something worth having looked at rather than left. So does a boiler that trips a specific error code repeatedly; most modern boilers display a code that a Gas Safe engineer can use to diagnose the fault before even arriving, which can save time and sometimes cost on the call-out.

Repair costs vary hugely depending on what is actually wrong, which is one of the reasons it is hard to give a single figure over the phone before an engineer has looked at the boiler. Minor faults, such as a faulty thermostat or a pressure issue, often cost somewhere around £80 to £200 to put right; moderate repairs, like a pump or valve replacement, more typically £200 to £400; and major work, such as replacing a heat exchanger, can run to £400, £1,000 or more depending on the boiler and how easily parts can be sourced. An emergency call-out for no heating or hot water often averages somewhere around £450, with a typical range of roughly £225 to £675, and Gas Safe engineers commonly charge somewhere around £50 to £80 an hour on top of parts.

A carbon monoxide alarm near the boiler, and ideally in any room with a gas appliance or flue, is a genuinely cheap and effective precaution, and it is worth checking it is in date and testing it periodically, the same way you would a smoke alarm.

If you are a landlord, a specific legal obligation applies on top of everything above, and this section is general information rather than legal advice — always check current requirements directly, for example via gov.uk, or with a solicitor or letting agent, since the detail can change. Landlords in the UK with a gas supply or gas appliances in a rental property are legally required to arrange an annual gas safety check, carried out by a Gas Safe registered engineer, and to provide the resulting certificate — commonly still referred to by its old reference, CP12 — to tenants. A copy must generally be given to a new tenant at the start of their tenancy, and to existing tenants within 28 days of the check being carried out, and landlords are typically expected to keep copies of gas safety records for at least two years. Failing to hold a valid, current certificate is not a minor paperwork issue: it can be treated as a criminal offence under health and safety legislation, with penalties that scale up sharply in the rare cases where a fault leads to injury or death.

Whether it is a routine annual service, a boiler that has stopped working properly, or arranging a landlord's gas safety check, the one constant is that only a Gas Safe registered engineer should ever be doing the actual gas work. Our directory lists plumbers and heating engineers covering towns and cities across the UK, so you can find someone local before your boiler picks the coldest week of the year to fail.

Frequently asked questions