Gas boiler displaying an error code or won't turn on – what to do?

Error codes on a gas boiler often indicate low water pressure, an ignition fault, or a blocked flue. First, check the pressure gauge: operating pressure should be between 1.0 and 1.5 bar – if it is below this, slowly top up the water via the filling valve until it reaches approximately 1.2 bar, then close the valve again. Next, restart the boiler using the reset button (press and hold for 3–5 seconds depending on the model). If the error persists or keeps reappearing, the cause may be a faulty sensor, a gas supply issue, or a flue fault – this must only be diagnosed and repaired by a registered heating engineer. Safety note: Never attempt to work on gas connections or burner components yourself.