Boiler not working? Common causes and what to check
Before you call anyone out, a few simple checks often explain why a boiler has stopped — and some you can safely sort yourself.
Safe checks you can do yourself
Start with the basics: is there power to the boiler, is the gas supply on (check other gas appliances work), and is the thermostat set above room temperature and calling for heat? A tripped fuse or a knocked thermostat is a surprisingly common culprit.
Next, check the pressure gauge. Most boilers run around 1–1.5 bar when cold; if it's well below 1, low pressure may be stopping the boiler firing, and topping it up via the filling loop often restores it.
Common causes of a boiler stopping
Frequent reasons include low system pressure, a fault code on the display, a pilot light that's gone out on older boilers, a frozen condensate pipe in cold weather (often a gurgling noise and a fault code), or radiators needing bleeding.
If your boiler shows a fault or lockout code, note it down — it helps the engineer diagnose the problem quickly.
When to call a Gas Safe engineer
If you smell gas, feel unwell, or see a yellow flame and sooty marks, treat it as urgent: turn the appliance off and call a Gas Safe registered engineer. If you smell gas, call the National Gas Emergency line on 0800 111 999.
For a boiler that won't restart after the basic checks, or repeated faults, it's best to have it looked at rather than keep resetting it. We'll diagnose the fault clearly and explain your options before doing any work.
Frequently asked questions
Why has my boiler stopped working?
Common causes are low pressure, a tripped fuse, a thermostat issue, a frozen condensate pipe in cold weather, or a fault/lockout code. Basic checks fix many of these; persistent faults need a Gas Safe engineer.
My boiler has no pressure — what do I do?
If the gauge reads well below 1 bar, you can usually top it up using the filling loop until it reaches around 1–1.5 bar. If it keeps dropping, there may be a leak and it's worth having it checked.
Is it safe to keep resetting my boiler?
Resetting once is fine, but repeatedly resetting a boiler that keeps locking out isn't advisable — the lockout is protecting you from a fault. Have it looked at instead.