Smell gas? Turn off the gas at the meter, open windows, don't switch anything electrical on or off, and call the National Gas Emergency line on 0800 111 999. Then call us once you're safe outside.
The 10-minute checklist
- Thermostat + programmer: confirm it's set above room temp and calling for heat. A flat thermostat battery is the single most common "boiler broken" call-out.
- Power: check the boiler's fused spur (usually next to it) and the consumer unit. RCDs sometimes trip after a power cut.
- Pressure gauge: combis need 1.0–1.5 bar cold. Below 0.8 → top up via the filling loop until it hits 1.2 bar. Above 2.5 → bleed a radiator to release excess.
- Frozen condensate pipe (winter): a white plastic pipe running outside. Pour warm — not boiling — water over the exposed section. Reset the boiler afterward.
- Fault code: write it down, then reset once. If it comes straight back, stop and call an engineer — repeated resets can damage the PCB.
Common fault codes translated
| Code (Worcester / Vaillant / Ideal) | What it usually means |
|---|---|
| F1 / EA / E133 | Ignition or flame failure — often a frozen condensate pipe in winter. |
| F22 / A02 | Low pressure — top up via the filling loop to 1.2 bar. |
| F75 | Pump / pressure sensor fault — needs an engineer. |
| F28 | Failed to ignite — check gas supply, then call an engineer. |
| H07 / SLF | Diverter valve or PCB — engineer job. |
Safe to try yourself
- • Repressurising via the filling loop
- • Bleeding radiators
- • Thawing an external condensate pipe
- • A single boiler reset
- • Replacing the thermostat battery
Call an engineer for
- • Any gas smell — do not troubleshoot
- • Water dripping from the boiler
- • Repeated fault codes after reset
- • Pilot light won't stay lit (older boilers)
- • Radiators cold at top / bottom after bleeding
When it's worth repairing vs replacing
Rough rule from 20+ years on the tools: if the repair is more than 40% of a new boiler price, and the unit is over 10 years old, replacement usually wins on cost, warranty and efficiency.
A modern A-rated combi typically saves £150–£300/yr in gas vs a 15-year-old non-condensing boiler, so the payback on a replacement can be 6–8 years even without the warranty peace of mind.
Related reading
Still stuck? Call us.
Radstock-based Gas Safe + OFTEC engineer covering Bath, Wells, Midsomer Norton and the Chew Valley. Fair, fixed diagnostic fee.