How often should a boiler be serviced?

The short answer for your situation

The yearly interval is the same for almost everyone with a domestic gas boiler. What changes is whether it is a legal duty, a warranty condition or simply good sense.

Is boiler servicing a legal requirement?

For owner-occupiers, no. You are not required by law to service your own boiler. You are, however, responsible for not using a gas appliance you know or suspect is unsafe, and a boiler that has not been looked at for years is much more likely to develop a fault you cannot see, including one that affects how it burns gas.

Landlords are in a different position. The law requires a gas safety check on every gas appliance and flue they provide at least every 12 months, carried out by a Gas Safe registered engineer, with a copy of the record given to tenants. Landlords must also keep those appliances maintained, and HSE's guidance points to the manufacturer's instructions for how. In practice most landlords book the annual service and the gas safety check on the same visit. Our guide to boiler service versus gas safety check explains how the two differ, and what certificates does a landlord need covers the rest of the paperwork.

Why once a year, and not every few years

A modern condensing boiler has parts that change slowly with use. Combustion settings drift, the condensate trap collects debris, seals age and the heat exchanger can pick up deposits. A yearly service catches these while they are small. The engineer takes flue gas readings, checks the flue route and seals, cleans what needs cleaning and checks the safety devices, then records what was done.

It is also about timing. Most boiler breakdowns happen when the heating is first asked to work hard in autumn and winter. A service in the warmer months finds worn parts before you rely on the boiler every day. The details of what happens during the visit are in our guide to how long does a boiler service take.

What a missed service does to your warranty

Boiler warranties are offered by the manufacturer, and their terms nearly always require the boiler to be serviced every year by a Gas Safe registered engineer, following their instructions, with the service recorded. If you then need to claim, the manufacturer may ask for those records. A gap can give them a reason to refuse.

Terms differ between brands and between warranty lengths, so read yours. Some allow a short window either side of the anniversary, others are stricter. Our guide on boiler warranty versus guarantee explains who stands behind what, and why keeping service paperwork in one place matters when you sell the home or change installer.

Register a new boiler with the manufacturer if your installer has not done it for you. An extended warranty often depends on registration within a set time after installation, as well as on the yearly service.

Can you leave it two years?

Nothing illegal happens if a homeowner leaves a boiler for two years, and plenty of boilers keep running. The honest risks are these: the warranty may lapse, the next service is more likely to find dirt or worn parts that take longer to put right, and a developing fault has a whole extra winter to become a breakdown.

If money is tight, the yearly service is usually cheaper than an emergency repair in January. If you do stretch it, do not stretch it when the boiler is showing any of the warning signs below.

When to get it checked sooner

Do not wait for the annual date if the boiler is behaving differently. Some of these signs point to a fault that needs a repair, not a routine service, and a few are safety issues.

• The flame looks yellow or orange instead of crisp blue, or there is soot or staining around the boiler
• Your carbon monoxide alarm sounds, or people in the home get headaches or feel sick that ease when they go out
• The pressure keeps dropping and you are topping it up often
• Kettling, banging or whistling noises from the boiler
• Repeated lockouts or fault codes that come back after a reset
• Water under the boiler or dripping from the condensate or pressure relief pipe
• The home has been empty for a long time, or there has been heavy building work and dust nearby

If you smell gas or suspect carbon monoxide, turn off the appliance if it is safe to do so, open windows, leave the property and call the National Gas Emergency Service on 0800 111 999. Do not use the boiler until it has been checked. Our guide to carbon monoxide signs at home explains the symptoms.

The best time of year to book

Late spring and summer are the easiest times to book a service. The heating is off or barely used, so having the boiler off for part of a visit is no hardship, and there is time to order parts if something is found. Early autumn is fine too, but it is when many people remember at once.

Whatever month you choose, keep to it every year. A fixed month makes it easy to stay inside warranty terms and, for landlords, keeps the gas safety record from lapsing. You can have a gas safety check done up to two months before the current record expires and keep the original expiry date, which makes it easier to line both jobs up.

Book your boiler service

Loyal Plumbers services boilers across London and inside the M25, and gas work is carried out by Gas Safe registered engineers. We can combine the service with a landlord gas safety check on the same visit, and we cover breakdowns 24/7 if the boiler fails in between.

Call us or send an enquiry with the boiler make and model, when it was last serviced, whether it is still under warranty and whether you also need a gas safety record. If the boiler is showing any of the signs above, tell us when you get in touch so we can treat it as a repair.