How long does a boiler service take?

Most people want to know how much of their day a service will take. For a typical gas boiler in a London home, plan for around an hour of the engineer working on the boiler, plus a little time either side.

A typical service, step by step

Stage	What happens
Arrival and chat	Engineer asks how the boiler has been running
Visual and gas checks	Looks at the boiler, pipework and gas pressure
Case off and inspection	Burner, heat exchanger, seals, electrodes, fan checked
Cleaning	Condensate trap and any deposits cleaned
Flue check	Inside and at the terminal outside
Combustion test	Flue gas analyser readings
Water side checks	Pressure, expansion vessel, controls, hot water flow
Write up	Service record and Benchmark section completed

Our post on what a boiler service includes explains each step.

What makes a service take longer

Getting to the boiler

This is the biggest factor in London. In converted Victorian houses, the boiler often ended up in a kitchen wall unit, a hall cupboard or a loft. Before the engineer can start, they may need to clear shelves, move stored things or set up a ladder.

You can help by:

• Clearing the cupboard around the boiler before the visit
• Moving anything stored under or beside it
• Making sure loft access has a safe ladder, boarding and light
• Clearing access to the gas meter

In Brixton, where many large houses are split into several flats, the gas meters are often grouped together in a front garden box or a shared hall. Knowing which meter is yours saves time. Our Brixton area page covers the conversions there.

Boiler type

A combi is usually the quickest to service. A system boiler with an unvented cylinder needs extra checks on the cylinder’s safety valves and expansion vessel. A regular boiler may have tanks in the loft to look at too. See system and regular boiler service.

Landlord gas safety checks

If you are a landlord and want the gas safety record at the same visit, every gas appliance and flue in the property must be checked. A boiler plus a hob is quicker than a boiler, a hob and a gas fire.

Parts and repairs

Some makers ask for certain seals to be replaced whenever the burner comes out. If the engineer finds a worn electrode, a blocked condensate trap or a flat expansion vessel, fixing it adds time. Most engineers carry common parts. Others need ordering.

Sludge and filters

If you have a magnetic filter, cleaning it adds a little time. If the system has a lot of sludge, the engineer may suggest further work, priced separately.

Hidden flues

In newer flats where the flue runs through a ceiling void, the engineer needs to inspect it through hatches. Opening and checking each hatch takes time. If there are no hatches, the HSE guidance says the boiler must be treated as at risk. Tell us when you book.

Why a very quick service is a warning sign

If an engineer arrives, glances at the pressure gauge, and leaves within a few minutes, that is not a service. Without the case off, nobody has looked at the burner, heat exchanger or seals. Without a combustion test, nobody has measured what the boiler is burning.

Signs a service was too short:

• No combustion readings on the record
• No mention of the case being removed
• No Benchmark entry
• Nothing written about the flue or condensate trap

Gas work in the UK must be done by a Gas Safe registered engineer. Ask for the ID card on arrival and check it on the Gas Safe Register. Our post on checking a Gas Safe engineer explains what the card should show.

Will I lose heating and hot water?

Yes, for part of the visit. The boiler is turned off while the case is off. Once it is back together, it is run and tested. If you work from home, plan to be away from the shower during the visit.

How to make the visit go smoothly

1. Give the make, model and age when booking.
2. Say where the boiler is and how to reach it.
3. Mention any problems: noises, pressure drops, fault codes, hot water issues.
4. Have the boiler manual ready if you can find it, so the Benchmark section can be filled in.
5. Tell us about parking. Many south London streets have controlled parking zones.
6. Clear the area around the boiler and the meter.

Timing your booking

Service visits are easier to schedule in spring and summer. Google search data for London shows demand in October at about four times the level of May and June. See our post on the best time to book.

When you book an annual boiler service, tell us about access and boiler type, and the visit can be planned properly.