Boiler Not Working London — 24/7 Emergency Repair

Before calling an engineer, check these four things: (1) Boiler pressure — look at the gauge on the front of the boiler. If it reads below 0.8 bar, low pressure may have caused a lockout. Repressurise to 1.0–1.5 bar using the filling loop under the boiler. (2) Boiler display — note any fault codes or warning lights (e.g. F22, EA, E1). These identify the fault type. (3) Thermostat — check your room thermostat or Nest/Hive app is set above the current room temperature and is calling for heat. (4) Gas supply — check other gas appliances (hob, gas fire) are working. If none work, you may have a gas supply interruption — call Cadent on 0800 111 999.

The most common fault codes we see on London boilers: F22 / 1017 (Worcester Bosch) = low pressure — repressurise to 1.2 bar; F28 / F29 = ignition fault — gas supply or spark electrode issue; EA = boiler lockout/overheat — reset and monitor; F75 = pressure sensor fault (often a failed sensor rather than actual low pressure); H07 = pump fault; E119 (Vaillant) = low pressure; F.83 (Vaillant) = temperature sensor fault. If the boiler shows a fault code and won't reset after two attempts, stop resetting — repeated reset attempts can mask a serious fault and damage the PCB.

Emergency boiler repair in London typically costs £80–£500 depending on the fault. Simple fixes (repressurise, reset, unblock condensate) cost £80–£150. Component repairs cost more: ignition electrode replacement £100–£180; diverter valve £150–£350; pump replacement £180–£350; PCB (control board) £200–£450; gas valve £200–£400. For boilers over 12–15 years old, we give honest advice about whether repair or replacement is the better value. Our call-out fee is £60, waived on jobs over 2 hours.

You can attempt one reset if the boiler shows a lockout (EA, E1, or similar). Hold the reset button for 3–5 seconds and wait 2–3 minutes. If the boiler fires and runs normally, monitor it for the next 24 hours. If it locks out again, do NOT keep resetting — call a Gas Safe engineer. Repeated resets on a faulty boiler can damage the PCB and turn a £150 repair into a £450 one. Never attempt to reset a boiler if you smell gas — leave the property and call Cadent on 0800 111 999.

If the boiler ignites (you can hear it fire) but radiators stay cold, the fault is downstream of the boiler: a seized circulation pump (the most common cause), a failed zone valve that isn't opening to the heating circuit, air locks in the system after topping up pressure, or a wiring fault at the room thermostat or timer. For hot water only (no heating): this classic pattern on a combi boiler points to a stuck diverter valve. For heating only (no hot water): the same diverter valve may be stuck in the heating position.

A useful rule of thumb: multiply the age of the boiler (in years) by the repair cost. If the result exceeds the cost of a new boiler (£2,000–£3,500 installed for a combi), replacement usually makes more financial sense. Specifically: boilers under 8 years old are almost always worth repairing. Boilers 8–12 years old: repair if the fault is a single component under £250; otherwise consider replacement. Boilers over 15 years: replacement is almost always better — parts become unavailable, efficiency drops to 70–78% vs 92–95% for a modern A-rated boiler. We give honest advice and won't recommend replacement unnecessarily.