What Does a Boiler Service Include?
Officially RegisteredA boiler service is a structured safety and performance check carried out by a Gas Safe registered engineer. It covers the boiler itself, the gas supply feeding it, the flue removing its fumes, and the controls that keep it operating safely — and it ends with a written record of everything that was tested.
The Six Steps of a Gas Safe Boiler Service
1Visual inspection of the boiler and flue
The engineer checks the boiler casing, seals and pipework for corrosion, leaks and signs of overheating, and confirms the flue is correctly fitted, unobstructed and terminating safely.
2Gas tightness and working pressure checks
A tightness test on the gas supply confirms there are no leaks, and the working pressure at the appliance is measured to make sure the boiler is getting the gas it was designed for.
3Combustion analysis
Using a flue gas analyser, the engineer measures the products of combustion to confirm the boiler is burning cleanly and efficiently, with no risk of carbon monoxide spillage.
4Cleaning of key components
The burner, heat exchanger, condensate trap and electrodes are inspected and cleaned where needed, and the condensate pipe is checked for blockages.
5Controls and safety device test
Thermostats, timers, pressure gauges, flame supervision devices and overheat stats are tested so the boiler shuts down safely if anything goes wrong.
6Report and service record
You receive a written record of what was checked, the combustion readings, and any defects or advisory work — your proof the boiler has been serviced by a Gas Safe registered engineer.
Why Each Check Matters
The visual inspection catches the problems you can see — corroded pipework, scorched casing, a flue that has worked loose. The tightness test catches the ones you cannot: even a small gas leak in a cupboard or plant room is dangerous. Combustion analysis is the heart of the service, because a boiler can look fine while burning badly, producing carbon monoxide or wasting gas.
Cleaning matters more than most people expect. A dirty burner or blocked condensate trap makes the boiler work harder, shortens its life and is one of the most common causes of winter breakdowns. Our Gas Safe registered boiler services follow this full sequence on every visit, domestic or commercial.
Domestic Boiler Services
For homeowners, an annual service keeps the manufacturer warranty valid — most makers require it — and is the single best way to avoid a midwinter breakdown. A combi boiler service typically takes 45 minutes to an hour and leaves you with a written record of the combustion readings and any advisory work.
If your boiler is getting older, a service is also the moment to get an honest view on whether repairs are still worthwhile. Our guide on how often you should replace your boiler explains the repair-vs-replace rule of thumb, and our guide to the benefits of a combi boiler covers what a modern replacement offers.
Commercial Boiler and Plant Servicing
Commercial boilers, warm air heaters and catering appliances work harder and are subject to stricter duties. Businesses must keep gas appliances safely maintained under the Gas Safety (Installation and Use) Regulations 1998, and insurers and environmental health officers routinely ask for service and safety records.
A commercial service covers the same core checks, scaled up: larger burners, additional safety shut-off devices, plant-room ventilation and flue systems. For commercial kitchens, the annual CP42 catering gas safety certificate combines the safety inspection with the service evidence your EHO expects to see.
Landlords: Service Plus CP12 Certificate
If you rent out a property, the law requires an annual gas safety check on every gas appliance you provide, carried out by a Gas Safe registered engineer, with the record given to your tenants. Most landlords combine the boiler service with this check in one visit.
Our CP12 landlord gas safety certificate service covers the boiler, hob and any other gas appliances in the property, and you can also book a combined boiler service and gas safety certificate so everything is done in a single appointment.
How to Book a Boiler Service
Booking is simple: call or send an enquiry, tell us the boiler make and model if you know it, and we will agree a visit time. The engineer carries out the full service, leaves a written record, and flags anything that needs attention with a fixed price before any extra work goes ahead.
Ready to book? Contact our Gas Safe engineers or see our published prices for standard visit rates.
Frequently Asked Questions
What does a boiler service include?
A Gas Safe boiler service includes a visual inspection of the boiler and flue, a gas tightness test, working pressure checks, flue gas combustion analysis, cleaning of the burner and heat exchanger, testing of controls and safety devices, and a written service record.
How long does a boiler service take?
A standard domestic boiler service usually takes 45 minutes to an hour. Commercial boilers and plant-room appliances take longer because of their size, additional safety devices and the testing required.
How often should a boiler be serviced?
Every 12 months. Annual servicing keeps the manufacturer warranty valid, catches worn parts early and is a legal requirement as part of a landlord's gas safety duties.
Is a boiler service different for landlords and homeowners?
The engineering checks are the same, but landlords must also hold a valid gas safety record (CP12) covering every gas appliance in the rented property, renewed every 12 months by a Gas Safe registered engineer.
What is checked on the flue and combustion during a service?
The engineer checks the flue is secure, correctly routed and unobstructed, then uses a flue gas analyser to measure carbon monoxide and carbon dioxide levels. Poor readings indicate incomplete combustion, which is a safety risk and must be put right.
Do I get a certificate after a boiler service?
Yes — you receive a written service record showing what was inspected, the combustion readings and any remedial work advised. Landlords receive a gas safety record (CP12) when the service is combined with the annual safety check.