The house is getting colder and the boiler has stopped. Start with the checks you can do without tools or opening the casing — then know when to leave it to an engineer.
Three things to know.
- Ensure the system pressure is between 1 and 1.5 bar
- Check that your thermostat has fresh batteries
- Note any fault codes to help your engineer diagnose the issue
01
The checklist
Work through these in order:
- Pressure: most sealed systems should read roughly 1–1.5 bar on the gauge when cold. Below that, the boiler may lock out — your manual shows how to top up with the filling loop.
- Power: is the fused spur switched on and the boiler display lit?
- Thermostat and timer: are they calling for heat? Check batteries in wireless thermostats.
- Gas: is there a known supply interruption? Check your supplier’s service updates without adjusting any gas fittings.
- Condensate pipe: in freezing weather, the outside plastic pipe may be frozen.
02
Write down the fault code
If the display shows a code, note it along with the boiler make and model. It helps an engineer diagnose the problem quickly and bring the right parts.
03
When to stop
If you smell gas, leave the property, don't use switches, and call the National Gas Emergency number on 0800 111 999. If the boiler is leaking or the pressure keeps dropping after topping up, call a Gas Safe registered engineer.
Further reading
For appliance-specific steps, follow your boiler or product manual. Work inside a gas boiler must be left to a Gas Safe registered engineer.
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