How Long Does a Boiler Service Take? 45 to 90 Minutes
Most boiler services take 45 to 90 minutes. What the engineer does in that time, what makes a service run longer, how to get ready for the visit and how often a boiler should be serviced.
A standard boiler service takes 45 to 90 minutes. A modern combi that is serviced every year and sits in an easy-to-reach kitchen cupboard is often done in about an hour. Older boilers, floor-standing and back boilers, boilers in lofts or tight cupboards, and boilers that have gone several years without a service take longer. If the engineer finds a fault, the repair is a separate job and adds time.
Key Takeaways
- Budget 45 to 90 minutes for a routine service; allow the whole morning or afternoon slot to be safe.
- Most of the time is spent on the safety checks and the flue gas analysis, not the cleaning.
- Clear access to the boiler, the flue and the gas meter before the engineer arrives.
- A service is not the same as a landlord gas safety check, although both can be done on one visit.
- Most manufacturers ask for an annual service to keep the warranty valid.
A boiler service usually takes 45 to 90 minutes. Most of that time goes on safety checks: the engineer inspects the boiler and flue, opens the case, cleans and checks the parts that wear, and takes a flue gas analysis reading to confirm the boiler is burning gas safely. A recent combi that is serviced every year tends to be at the quicker end. An older boiler, a back boiler, or one that has not been serviced for a few years is likely to take longer.
If you are booking a service and want to know what it costs rather than how long it takes, our boiler service cost guide covers what is included and what can cost extra.
Typical boiler service timings by boiler type
These are typical ranges for a routine annual service where nothing major is wrong. They do not include any repair work the engineer recommends afterwards.
| Boiler and situation | Typical time | Why |
|---|---|---|
| Modern combi, serviced last year, easy access | 45 to 60 minutes | Few deposits to clean, parts easy to reach |
| System or regular boiler with a cylinder | 60 to 75 minutes | More controls and components to check |
| Boiler not serviced for several years | 75 to 90+ minutes | Heavier cleaning of the burner, heat exchanger and condensate trap |
| Floor-standing or back boiler | 60 to 90+ minutes | Older designs, harder access, often behind a gas fire |
| Boiler in a loft or tight cupboard | Add 15 to 30 minutes | Access, lighting and working space |
Treat these as a guide rather than a promise. Two boilers of the same model can take very different times if one sits in a clean kitchen cupboard and the other is in a dusty loft with a long flue run.
What happens during a boiler service
Knowing the steps makes it easier to see where the time goes, and to spot a service that has been rushed.
Visual check and questions
The engineer asks about any faults, pressure drops or noises, then looks over the boiler, the pipework, the flue and the area around it for signs of leaks, scorching or poor installation.
Flue gas analysis
With the boiler running, a flue gas analyser measures what is coming out of the flue. This shows whether the boiler is burning gas cleanly and safely, and it is one of the most important readings on the service record.
Case off, inspect and clean
The boiler is isolated and the case removed. The engineer inspects and, where needed, cleans the burner, electrodes, fan, heat exchanger and condensate trap, and checks seals and gaskets.
Gas and safety device checks
Gas pressure and gas rate are checked against the manufacturer's figures, and safety devices are tested to make sure the boiler shuts down when it should.
Flue and ventilation
The flue is checked along its visible length and at the terminal outside for damage, blockage and correct clearances from windows and doors.
Reassemble, test and record
The boiler is reassembled, fired up, checked for gas tightness and tested on heating and hot water. You should get a written service record and a note of anything that needs attention.
Some engineers also check the system pressure and the expansion vessel charge as part of the service. Recharging or replacing an expansion vessel, flushing a sludged system or replacing worn parts is normally quoted as extra work. If the pressure keeps dropping between services, our guide to why a boiler loses pressure explains the usual causes.
What makes a boiler service take longer
- Years without a service. Deposits build up on the burner and heat exchanger and the condensate trap can partly block, so there is more to clean.
- Access. Boilers in lofts, behind fitted units or in small airing cupboards take longer to open up and work on. Long or boxed-in flues take longer to inspect.
- Older or unusual boilers. Back boilers, floor-standing models and older non-condensing boilers can involve more parts and more careful checks. See our back boiler page if yours sits behind a gas fire.
- A fault found during the service. If a reading is out, a seal is perished or a part has failed, the engineer will explain it and quote for the repair. Minor adjustments may be done on the day; a replacement part may need a return visit.
- Extra appliances. If you also want a gas hob, gas fire or a landlord gas safety check done, allow more time.
How to prepare so the service goes quickly
- Clear the space. Empty the boiler cupboard, move anything stored under or around the boiler, and make sure the loft hatch and ladder are usable if the boiler is up there.
- Make the flue terminal reachable. The engineer needs to see where the flue comes out outside. Tell them when booking if it is above a conservatory roof or out of sight.
- Find the gas meter. The engineer may need to check the gas pressure at the meter, so make sure the meter cupboard key is to hand.
- Have the paperwork ready. The last service record and the boiler manual, if you have them, save time and help with warranty checks.
- Note any faults. Write down any error codes, noises or pressure drops so the engineer can look at them while the case is off.
Ask when you book whether the engineer would like the heating left on or off beforehand. Some prefer a warm boiler for the combustion test, others would rather the parts had cooled before they work inside it.
Boiler service vs gas safety check
A service and a gas safety check overlap, but they are not the same thing. A service looks after the boiler: cleaning, adjusting and checking it is working as the manufacturer intended. A gas safety check, which is what landlords need every year for a gas safety certificate (CP12), is a safety inspection of every gas appliance, flue and the gas pipework in the property. It does not include cleaning or servicing the boiler.
Landlords often book both on one visit. That is sensible, but it takes longer than a service alone because every gas appliance in the property has to be checked and recorded. Our gas safety certificate guide explains what the check covers and what landlords must do with the record.
How often should a boiler be serviced?
Once a year is the standard advice from boiler manufacturers and from the Gas Safe Register. Most manufacturer warranties require an annual service by a Gas Safe registered engineer, and a missed service can give the manufacturer grounds to refuse a warranty claim. Keep every service record in one place.
The quickest time to book is late summer or early autumn, before the heating goes on full-time. From November engineers are busier with breakdowns, and a boiler that has not been checked is more likely to be one of them. If your boiler is already showing faults, a service may not be the right booking: ask for a boiler repair visit instead so the engineer comes prepared to diagnose it.
Want your boiler serviced before winter?
Tell us the boiler make and model and where it is installed. We'll book a Gas Safe registered engineer and confirm the price before the visit.
📞 Call 020 7870 3200Or read more about our London boiler service.
Frequently Asked Questions
How long does a boiler service take?
Most boiler services take between 45 and 90 minutes. A well-maintained modern combi is often done in about an hour, while older, floor-standing or neglected boilers, and boilers in awkward places, can take longer.
Do I need to be at home for a boiler service?
Someone over 18 needs to let the engineer in and be available at the end so the engineer can explain what was found. In rented homes the landlord or agent can arrange access, but the tenant should agree the appointment.
Will I have heating and hot water during the service?
The boiler is switched off while the engineer works inside it, so you will be without heating and hot water for most of the visit. It is switched back on and tested before the engineer leaves, unless it is found to be unsafe.
Is a 20-minute boiler service too quick?
It is hard to carry out the full set of checks, including opening the case, testing the flue and taking a flue gas analysis reading, in 20 minutes. If a visit is that short, ask the engineer which checks were done and ask for the written service record.
How long does a boiler service and gas safety check take together?
Doing both on one visit usually adds around half an hour or more to the service, depending on how many gas appliances are in the property, because every appliance, flue and the pipework need checking for the certificate.
Sources and further reading
Source links checked 27 September 2026. Scheme rules and manufacturer instructions can change; use the current official guidance for your account or exact appliance.