A gas boiler should be serviced once every twelve months, without exception. Manufacturers require it to keep the warranty valid, landlords are legally required to have gas appliances checked annually, and the parts that fail in winter are almost always the ones a service would have caught in September. A boiler that has been serviced every year typically lasts longer, uses less gas and breaks down less often than one serviced only when it goes wrong.
This guide explains why the interval is a year, what the service actually protects, the best time to book, and the practical consequences of skipping it.
Why every twelve months
Safety
Combustion drifts. Seals age, heat exchangers scale, flues get blocked by nests and debris, and a boiler that was burning cleanly a year ago can be producing carbon monoxide now. The annual combustion test with a flue gas analyser, the flue inspection and the safety device checks are what catch it.
Warranty
Almost every manufacturer’s warranty, whether two years or twelve, is conditional on an annual service by a registered engineer with the record kept. Miss a year and a claim in year four can be refused. Our guide to boiler warranties explains the conditions.
Efficiency
A clean burner, a clean heat exchanger and correctly set combustion mean more of the gas becomes heat. A neglected boiler slowly loses efficiency and the bills creep up without any change in how you use the heating.
Reliability
Fans, electrodes, pumps, diverter valves and expansion vessels give warning before they fail, and a service is where an engineer sees the warning. Replacing a part in September on a planned visit is cheaper and calmer than replacing it in December on an emergency call.
The best time to book
Late summer or early autumn. The heating is off, so a fault found on the day is no hardship; engineers have room in the diary; and the boiler goes into winter checked. Spring is the next best, straight after the heating season. December and January are the worst, because every engineer is on breakdowns and a routine service waits. Our guide to preparing your boiler for winter lists the other autumn checks.
What a proper service includes
A visual inspection of the boiler, flue and pipework; the casing off and the burner, heat exchanger, electrodes, seals, fan and condensate trap inspected and cleaned to the manufacturer’s schedule; a gas pressure check; a combustion test with an analyser; safety devices, the expansion vessel and the relief valve checked; the magnetic filter cleaned; the pressure topped up; and the record completed. It takes 30 to 60 minutes. A ten-minute visit with the casing left on is not a service. Our guide to how long a boiler service takes goes through it.
Landlords
Landlords must have a gas safety check on every gas appliance every twelve months and give tenants the record. The check and the service are different jobs, but most engineers do both in one visit. Our guide to the landlord gas safety certificate explains the duty.
What happens if you skip a year
- the warranty may be void for any claim that follows
- a developing fault goes unnoticed until it stops the boiler, usually in winter
- efficiency drops and gas use rises
- a combustion or flue problem goes undetected, which is the safety risk
- on a rented property, the landlord is breaking the law
New boilers
A new boiler needs its first service within twelve months of installation, not twelve months of first use, to keep the warranty. Put the anniversary in the diary on the day it is fitted. Our guide to what is included in a new boiler installation explains the handover paperwork that records the date.
Oil boilers
The same rule, every twelve months, for the same reasons, plus a new nozzle and filter and a tank check. Our guide to how often an oil boiler should be serviced covers the oil-specific points.
How DCI Boilers can help
DCI Boilers services gas boilers across Cornwall and Devon with Gas Safe registered engineers who service to the manufacturer’s schedule, test combustion every time and show you the readings, at a fixed price. Book your boiler servicing visit for late summer and we will remind you next year. Anything we find is quoted at a fixed price for boiler repairs, with no pressure to proceed.
Need help now? Call DCI Boilers on 07888 862 603 or get a free quote.
Frequently asked questions
Is it a legal requirement to service a boiler every year?
For landlords, an annual gas safety check is the law. For homeowners it is not a legal duty, but it is a warranty condition and the only reliable safety check.
Can I service a boiler every two years instead?
You can, but the warranty will lapse and faults develop unseen. Every twelve months is the standard for good reason.
Does a new boiler need servicing in its first year?
Yes, within twelve months of installation, to keep the warranty valid.
What month is best for a boiler service?
August or September, before the heating season and while engineers have space in the diary.