How long does a boiler service take by boiler type?
How long a boiler service takes depends mainly on the type of boiler and its condition. A combi keeps almost everything inside one case, so it is the quickest. System and regular boilers have more parts around them to check, and oil boilers have a burner with parts that are replaced every year.
| Boiler type | Typical service time | Why |
|---|---|---|
| Gas combi | Around 30 minutes to 1 hour | Everything is in one case; the engineer also checks the hot water side |
| Gas system boiler | Around 1 hour | Pump and expansion vessel in the boiler, plus a hot water cylinder to look at |
| Gas regular (heat only) | Around 1.5 hours | Older designs, separate pump and valves, feed and expansion tank in the loft |
| LPG boiler | Similar to the gas equivalent | Same boilers and tests, with LPG gas pressures |
| Oil boiler | Around 1 to 2 hours | Burner removed, nozzle and filter replaced, heat exchanger cleaned, tank checked |
Figures are based on the Checkatrade and Energy Saving Trust guides to boiler servicing. Treat them as a starting point: Checkatrade notes that age and condition matter more than boiler type, and that a combi needing thorough attention can take up to 90 minutes instead of 30.
If you are not sure which type you have, our guide to the combi boiler explains how to tell a combi from a system or regular boiler. If you have an unvented hot water cylinder, which is common with system boilers, manufacturers generally ask for its safety valves to be checked every year by someone qualified for unvented work. When your engineer does that at the same visit, allow extra time.
What happens during the visit, stage by stage
A service moves between the boiler running and the boiler switched off. That is why you may have hot water for part of the visit and not for the rest. The full list of checks is in our guide to the annual boiler service; this table shows how the time is spent.
| Stage | Boiler | Hot water on a combi |
|---|---|---|
| Questions, service history and visual checks of the boiler, pipes and flue | On | Available |
| Flue gas analysis and gas pressure tests | Running, often at full output | The engineer may run a hot tap to fire the boiler |
| Case off: burner, heat exchanger, electrodes, fan and condensate trap inspected and cleaned | Gas and power isolated | Not available |
| Water side: pressure, expansion vessel, filter | Usually off | Not available |
| Reassembly, leak check and final tests | Back on | Available again |
| Paperwork and advice | On | Available |
What can make a boiler service take longer
A service takes longer when the engineer finds something that needs more than the routine checks. The common reasons are:
- Poor combustion readings. If the flue gas analyser shows too much carbon monoxide, the engineer has to take the burner out and clean or reset parts, then test again.
- An older or dirty boiler. Heavy deposits on the heat exchanger or a condensate trap full of sludge take time to clear.
- Parts that need replacing. Seals and gaskets disturbed during the service may need renewing. If a larger part is needed and not in the van, the job may need a second visit.
- A magnetic filter clean. A heavily loaded magnetic filter has to be isolated, emptied and refilled, which adds time.
- Expansion vessel recharge. If the vessel has lost its charge, the boiler side has to be drained to check and recharge it. Our guide to the expansion vessel explains why.
- Tight access. A boiler boxed into a narrow cupboard, or with shelves and boxes in front, slows everything down. See our guide to the boiler cupboard for the service clearances manuals ask for.
- Extra appliances. Adding a landlord gas safety check on a hob, cooker or gas fire adds time for each appliance.
- A first visit. An engineer who has not seen your system before may spend longer finding valves, the gas meter and the flue route.
Checkatrade notes that most services are charged at a fixed price rather than by the hour, so a longer visit does not usually cost more unless parts are needed. Our boiler service cost guide covers what is normally included.
How long does it take to service an oil or LPG boiler?
An oil boiler service usually takes around 1 to 2 hours, longer than a gas service. The technician removes the burner, replaces the nozzle and fuel filter, cleans the heat exchanger and checks the oil tank and supply line, then runs combustion tests. Some technicians ask you to switch the boiler off before they arrive so it has cooled, so ask when you book. An LPG boiler takes about as long as the same type of mains gas boiler. Our guide to oil and LPG boiler servicing covers what each involves.
Do I need to be home for a boiler service?
Yes, someone usually needs to be home for a boiler service. Most engineers and service companies need an adult to let them in, show them the boiler, gas meter and controls, and sign or receive the paperwork. It does not have to be the homeowner; a trusted adult can wait in for you.
If you rent, your landlord or letting agent normally arranges the visit and should give you notice. You need to allow access, but you can agree a time that suits you. Whoever is home should ask to see the engineer's Gas Safe ID card before letting them start.
Can I use hot water during a boiler service?
You can use hot water for part of the service, but not while the boiler is switched off for the inside inspection. On a combi, that means no hot water at all during that stage. Ideal's servicing advice says you may be without hot water for an hour or two, while cold water stays available throughout.
If you have a system or regular boiler with a hot water cylinder, the water already stored in the cylinder stays hot while the boiler is off, so you can usually still run a hot tap. Avoid running a bath or shower during the tests unless the engineer asks you to, as it changes how the boiler fires and can affect the readings.
How to prepare for the engineer
- Clear the cupboard around the boiler and the path to it.
- Make sure the engineer can reach the gas meter, the flue terminal outside and, for a regular boiler, the loft tank.
- Find the boiler manual with the Benchmark service record, and your last service paperwork.
- Note any fault codes, noises or pressure drops since the last service.
- Keep pets and children out of the way while the case is off.
Mention any faults when you book. Checkatrade suggests this so the engineer can allow extra time. It also gives them the chance to bring likely parts, which can save a second visit.
What to do if the service seemed too quick
A combi service in 30 minutes can be done properly, but a visit where the engineer never uses a flue gas analyser, never takes the case off and leaves no written record is not a full service. If that happens, ask what was checked and ask for the readings. If you are not satisfied, contact the company, and if your boiler is under guarantee, check the manufacturer's terms before booking the same engineer again. For landlords arranging combined visits, our guide to gas safety certificate costs explains how the safety check differs from a service.