5 min read
Boiler Not Working? 6 Common Faults and What They Mean
No heating or hot water? Before you call, here are the most common boiler faults in Irish homes, what causes them, and which you can safely check yourself.
Low boiler pressure
If the pressure gauge reads below about 1 bar, your boiler may lock out. This is often caused by a small leak in the system or bleeding radiators. You can usually top it up using the filling loop, but if it keeps dropping there is a leak that needs finding.
No hot water but heating works (or vice versa)
This often points to a faulty diverter valve or motor. It is a common, repairable fault — the valve directs water between heating and hot water, and when it sticks you lose one of the two.
Boiler locks out with an error code
Modern boilers show a fault code on the display. Note it down — it tells the engineer a lot before they arrive. A quick reset sometimes clears it, but repeated lockouts mean a fault that needs diagnosis.
Radiators cold at the bottom or top
Cold at the top usually means trapped air — bleed the radiator. Cold at the bottom usually means sludge build-up, which may need a power flush to restore efficiency.
Frozen condensate pipe
In cold weather the external condensate pipe can freeze, causing a lockout. Thawing it gently with warm (not boiling) water often gets the boiler going again.
Strange noises (banging, gurgling, whistling)
Kettling noises usually indicate limescale or sludge on the heat exchanger. It is worth addressing early, as it makes the boiler work harder and shortens its life.
