Boiler repair in London
No heat or hot water? We diagnose the fault on site and tell you what it costs before anything is fitted.
Service overview
Boiler repair is the job we get called out for most. A lockout, a leak or a boiler that will not fire usually needs someone on site the same day rather than a week of phone calls.
We diagnose the fault first, explain what has failed and what it takes to put right, then fit parts you have agreed to. If a repair is not worth doing on an old appliance we will say so rather than sell you a part that buys three months.
Most domestic boilers in London are combis under 30kW, and most of what stops them is a short list: pressure loss, a failed expansion vessel, a stuck diverter valve, a blocked condensate or an ignition fault. None of those need a new boiler.
We work across Greater London and north Surrey, including Croydon, Bromley, Sutton, Orpington and Wimbledon. Gas Safe engineers do every gas job. See the gallery, about us or get in touch.
Get a quoteSigns you need boiler repair
- No heat and no hot water, with a code on the display
- Pressure gauge sitting below 0.7 bar, or climbing above 2.5 bar when hot
- Boiler fires then cuts out after a few seconds
- Hot water works but the radiators stay cold
- Water dripping from the bottom of the case or from the pressure relief pipe outside
- Banging or kettling from the boiler when it fires
What usually goes wrong
A sealed heating system should sit at roughly 1.0 to 1.5 bar when cold. Below about 0.7 bar most boilers lock out on low pressure and refuse to fire. Sometimes that is a genuine leak, and sometimes it is an expansion vessel that has lost its air charge, which makes the pressure swing high when hot and low when cold. Those two faults look identical on the gauge and need completely different work, so the vessel gets checked before anyone starts hunting for a leak.
The other common group is ignition. The boiler tries to light, fails to prove a flame, and locks out. That can be the electrode, the gas valve, a blocked flue or a condensate pipe that has frozen and backed up. Condensate blockages spike every winter because the pipe often runs outside in 22mm plastic when it should have been sleeved or run internally.
Repair or replace
The honest test is the cost of the part against the age and condition of the appliance. A ten-year-old boiler needing a fan and a gas valve on the same visit is usually worth replacing. A six-year-old boiler needing a pressure relief valve is worth repairing without question.
Manufacturer warranties run between five and twelve years on new installs, but they are conditional on a documented annual service. If your boiler is still inside its warranty period, tell us before we start — the fault may be the manufacturer's to fix, and we would rather point you at that than charge you for it.
Common fault codes
If your boiler is showing a code, read it out when you call. It usually tells us which parts to put on the van.
| Code | Make | What it means | Where we start |
|---|---|---|---|
| F.22 | Vaillant | Low water pressure, or a dry fire condition | Check for a leak, then test whether the expansion vessel is holding its charge before repressurising |
| F.75 | Vaillant | Pump or pressure sensor fault | Common straight after a filter clean or a drain-down; usually air in the pump head or a failed sensor |
| F.28 | Vaillant | Ignition failure — the boiler never proves a flame | Gas supply, electrode and gas valve checked in that order |
| EA | Worcester Bosch | Flame loss or ignition lockout | Electrode gap, condensate blockage, or gas supply pressure at the appliance |
| C6 | Worcester Bosch | Fan fault — fan speed outside the expected range | Fan, wiring or the air pressure switch |
| E9 / D5 | Worcester Bosch | Overheat — the primary is getting too hot | Usually poor circulation: a stuck pump, a closed valve or a sludged heat exchanger |
| F1 | Ideal | Low water pressure | Same route as F.22 — find the reason before topping up |
| L2 | Ideal | Ignition lockout | Flame sensing, gas supply or a blocked condensate |
| E119 | Baxi | Low system pressure | Leak test, then expansion vessel charge |
How the visit goes
Tell us the code
If there is a code on the display, read it out when you call. It often tells us which parts to bring.
Diagnose on site
Gas pressure, system pressure, flue integrity and the actual fault, before anything is quoted.
Agree the work
You get the cost of the repair and the honest repair-or-replace view before a single part is fitted.
Test and leave it working
Combustion checked, pressure set, and the system run up to temperature before we go.
Standards this work is held to
Gas Safe Register
Only a Gas Safe registered engineer may legally work on a gas appliance. The register replaced CORGI in April 2009.
Nominal working pressure 20 mbar
Natural gas at the appliance inlet should run at about 20 mbar under load. A boiler starved of gas will lock out and keep locking out until that is fixed.
Benchmark
Warranty claims usually depend on a completed Benchmark commissioning record and a documented annual service.
Boiler repair: common questions
Related to Boiler repair
Areas we cover
We work across Greater London and north Surrey, including Croydon, Bromley, Sutton, Orpington and Wimbledon. Pick your town.
Need an emergency plumber?
Burst pipes, boiler breakdowns and blocked drains across Greater London. We aim to be with you within 60 minutes.