How long does a boiler service take?

What the engineer does during the service

Most of the visit is spent checking that the boiler burns gas safely and efficiently, and that it gets rid of its combustion products properly. The exact steps depend on the manufacturer's instructions for your model, which is why an engineer may do things slightly differently on a Vaillant than on a Worcester Bosch or an Ideal.

A typical service follows the pattern below. Some steps take a couple of minutes, others take longer when the boiler is dirty or a reading is out of range.

Why some services take much longer

The time on the booking is for a routine service. It is not a promise that nothing else will be found. If the engineer finds a fault, the visit becomes partly a repair visit, and how long that takes depends on the part and whether it is on the van.

A boiler that has gone several years without a service is the most common reason for a long visit. The condensate trap may be blocked, the heat exchanger dirty and the combustion readings poor, all of which take time to put right before the boiler can be signed off.

• The boiler is inside a tight cupboard, above a fitted unit or in a loft with poor access
• The flue runs through a ceiling void with no inspection hatches
• Combustion readings are outside the manufacturer's limits
• The condensate trap or pipe is blocked
• System pressure keeps falling, or the expansion vessel needs recharging
• A landlord gas safety check on other appliances is added to the same visit
• Service records are missing and the history has to be worked out from the boiler itself

If an engineer finds something unsafe, they may turn off the appliance and label it rather than finishing a normal service. That is a safety decision, not a delay. Ask them to explain the finding and write it down.

Service and landlord gas safety check on the same day

A boiler service and a landlord gas safety check are different jobs, although they are often booked together. The service follows the manufacturer's maintenance instructions for the boiler. The gas safety check covers every gas appliance and flue the landlord provides, and produces the record a landlord must keep and give to tenants.

Combining them saves a second visit, but it adds time. A flat with just a boiler adds little. A house with a gas hob, a gas fire and a boiler adds a check on each one. Our guide on boiler service versus gas safety check explains what each document records.

How to keep the visit short

Most of the time lost on a service is lost before the engineer starts. Clear the boiler cupboard, make sure the flue can be seen along its whole route where possible, and know where the gas meter is. If the boiler is in a loft, check there is safe access, boarding and light.

Have the boiler manual and previous service records ready if you have them. They tell the engineer what was done last time and help with the warranty paperwork. If the boiler has been showing a fault code, losing pressure or making a noise, mention it when you book, so the engineer can plan for it rather than discover it halfway through.

• Clear shelves and stored items from around the boiler
• Make sure lofts and cupboards are safely accessible and lit
• Know where the gas meter and the heating controls are
• Keep the manual and past service records to hand
• Tell us about any fault codes, pressure loss or noises when you book

Do you need to be at home, and can you use the heating?

Someone needs to let the engineer in and be available at the end, when they explain what they found and hand over the service record. You do not need to watch the whole service.

The boiler is switched off for part of the visit, so you will be without heating and hot water for a while. Once the engineer has finished and tested it, you can use it normally. If they have had to leave it switched off for safety reasons, do not turn it back on until the fault has been repaired.

Book a boiler service

Loyal Plumbers services boilers across London and inside the M25, with gas work carried out by Gas Safe registered engineers. We run 10 vans, so we can usually offer a time that suits you, and we cover heating breakdowns 24/7 if something goes wrong before then.

Call us or send an enquiry with the boiler make and model, where it is installed, when it was last serviced and whether you also need a landlord gas safety record. That helps us give you a realistic time for the visit before we arrive.