Boiler Service London: Gas Safe Annual Checks

London's water is hard. Thames Water, which supplies most of the capital, puts all of its supply in the hard or very hard band, and that matters most for a combi. The hot water side of a combi heats mains water directly, so scale settles on the plate heat exchanger, flow drops and the boiler burns more gas for the same shower.

An annual service is the cheapest moment to catch it. An engineer can spot a sluggish heat exchanger or a clogged filter months before it becomes a breakdown in January.

London at a glance

Water hardness: Hard. Thames Water, which supplies most of London, says all the water in its region is hard (200 to 300 mg/l of calcium carbonate) or very hard (over 300 mg/l). Source
Private renting: 30.0% of London households rented privately in 2021, the highest share of any region. Source
Landlord gas checks: Landlords must have every gas appliance and flue checked by a Gas Safe registered engineer every 12 months, give tenants a copy and keep the record for 2 years. Source

What happens on the visit

Expect the casing off, a look at the burner and heat exchanger, a flue gas analysis, and tests on the gas pressure, safety devices and condensate pipe. In a London flat the flue often runs through a ceiling void to a lightwell, so the engineer needs to see the full run, including any inspection hatches.

Ask for the service to be written up in the boiler's logbook. Most manufacturers make a yearly service a condition of the warranty, and a lapse can be enough for a claim to be turned down.

If you let a home

About three in ten London households rent privately, a higher share than any other region in the 2021 Census. As a landlord, HSE rules require a Gas Safe engineer to check every gas appliance and flue in the property every 12 months.

Existing tenants must get a copy of the record within 28 days, new tenants before they move in, and you keep it for two years. A gas safety check is not a full service, so ask for both on the same visit if you want the boiler maintained as well as certified.

HSE lets you book the check up to two months early and keep the original anniversary date, which helps when tenants are hard to pin down.

Tenants: who books it

If you rent, the landlord or letting agent arranges and pays for the gas safety check. Your part is letting the engineer in. If the anniversary passes with no visit, tell your landlord in writing and keep a copy.

Servicing in London's housing

Victorian and Edwardian terraces

Many terraces had the boiler moved to the loft during a refit. A loft boiler needs a fixed ladder, boarding and a light; without them some engineers won't go up, so sort out access before the appointment.

Converted flats and mansion blocks

The boiler is usually boxed into a kitchen cupboard. Empty the cupboard beforehand and check the engineer can see the flue terminal outside, from a window or the garden.

Outer-borough 1930s semis

Semis often keep a regular boiler with a hot water cylinder in the airing cupboard. Ask for the cylinder thermostat and motorised valves to be checked too, since they fail more often than the boiler.

Areas covered

Engineers who cover London work across areas including Islington, Hackney, Camden, Brixton, Wimbledon, Ealing, Croydon, Walthamstow, Greenwich and Richmond.

View London on Google Maps

Questions people in London ask

Does hard water mean I need a service more than once a year?

No. Once a year is still the norm. Hard water is a reason not to skip a year, because scale damage builds slowly and is easy to miss until hot water flow drops.

Should I add a scale reducer to my combi?

If there is nothing fitted on the cold main feeding your combi, ask the engineer whether one suits your model. On an existing boiler it is a small plumbing job, and our boiler service guide explains what else to ask about.

Sources

Also nearby: Boiler servicing in Reading, Boiler servicing in Luton, Boiler servicing in Chelmsford, Boiler servicing in Brighton

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