Common Boiler Error Codes Explained: What They Mean and What to Do
Modern boilers display error codes on their digital screens when something goes wrong. While the specific codes vary between manufacturers, many of the underlying faults are the same. This guide covers the most common boiler error codes homeowners in {location} encounter and what you should do about them.
Low Boiler Pressure (F1, F22, E119, CE 207)
This is the single most common boiler fault. Your boiler needs water pressure between 1.0 and 1.5 bar to operate. If pressure drops too low, the boiler locks out for safety.
- Quick fix: Repressurise the system using the filling loop underneath the boiler. Open the valve slowly until the gauge reads 1.2–1.5 bar, then close it
- If it keeps dropping: You likely have a leak in the system — check radiator valves, pipe joints, and the pressure relief valve. Call a Gas Safe engineer if the problem recurs
Ignition Failure (F28, F29, E133, EA 338)
The boiler is trying to fire up but can't ignite. This can be caused by:
- A faulty ignition electrode or lead
- Gas supply issues — check other gas appliances are working and that the gas meter valve is open
- A blocked or frozen condensate pipe (see below)
- A faulty gas valve within the boiler
What to do: Reset the boiler once. If it fails again, do not keep resetting — call a Gas Safe registered engineer in {location}.
Frozen Condensate Pipe (F28, F29, D3, EA)
Condensing boilers produce acidic water that drains through a small plastic pipe, usually exiting through an outside wall. In freezing weather, this pipe can ice up and block, causing the boiler to shut down.
- Quick fix: Pour warm (not boiling) water over the external section of the condensate pipe to thaw it. Reset the boiler
- Prevention: Ask your engineer to lag the condensate pipe or reroute it to an internal drain
Fan Fault (F33, F34, E160)
The fan must run before the gas valve opens — this ensures combustion gases are safely expelled. A fan fault code usually means the fan has failed or the boiler's PCB can't detect it running.
What to do: This requires a Gas Safe engineer. Do not attempt to bypass or repair boiler fans yourself.
Overheating / High Temperature (F20, E125, D1)
The boiler has detected that the water temperature is dangerously high and has shut down to prevent damage.
- Could be caused by a blocked pump, sludge in the heat exchanger, or a faulty thermostat
- Do not reset repeatedly — overheating can damage the heat exchanger, which is one of the most expensive boiler components to replace
- Call a Gas Safe registered engineer immediately
General Guidance
- One reset is fine. If the error returns after resetting, don't keep trying — you could make the problem worse
- Note the exact error code and any numbers on the display before calling an engineer — this helps them prepare the right parts
- Check your boiler manual — most manufacturers also have online code lookup tools
- Only use Gas Safe registered engineers — it's illegal for anyone else to work on gas appliances, and it voids your warranty
Regular annual servicing by a Gas Safe engineer in {location} is the best way to catch developing faults before they trigger error codes and leave you without heating or hot water.