Boiler breakdowns peak in November and December — not because boilers suddenly fail, but because problems that existed all summer go unnoticed until the heating is needed. A bit of preparation in September or October saves a lot of hassle.
Here's what to check.
1. Turn the heating on before you need it
The most basic check. Run the heating for an hour in September, while it's still warm enough that you don't need it. You'll find out if anything isn't working before it becomes urgent.
Check that:
- Every radiator heats up (cold spots mean bleeding or balancing is needed)
- The boiler fires without any unusual noises
- The thermostat responds correctly
- The boiler pressure stays in the normal range (1–1.5 bar) during operation
2. Check the boiler pressure
Cold system pressure should sit between 1 and 1.5 bar. If it's below 1, the boiler may lock out when you need it. If it drops repeatedly, there's a slow leak somewhere that needs finding before winter.
How to check: look at the pressure gauge on the boiler (usually on the front or bottom). If it needs topping up, repressurise via the filling loop — see our guide on boiler pressure.
3. Bleed the radiators
If radiators have cold patches at the top, they have trapped air. Bleeding them now means the system heats evenly when you need it. Start with the radiator furthest from the boiler.
After bleeding, remember to check and top up boiler pressure — bleeding releases water along with the air.
4. Check the condensate pipe
Condensing boilers produce wastewater that drains through a condensate pipe, usually to an external drain. In freezing temperatures, this pipe can freeze — causing the boiler to shut down safely.
If your condensate pipe runs externally, it's worth insulating it before the cold weather arrives. It's one of the most common causes of boiler lockouts in January.
5. Test your thermostat and controls
Set the thermostat to a temperature above the current room temperature and confirm the boiler fires. If you have a smart thermostat, check the schedule is set up correctly for the coming months.
If the thermostat isn't responding or the boiler isn't firing when it should, better to find out now.
6. Book a service
If the boiler hasn't been serviced in the last 12 months, book one before October. Engineers get booked up quickly as the weather turns — waiting until November often means a 2–3 week wait.
A service will catch anything that's developing as a problem and give you confidence the boiler will perform through winter.
7. Know where your stopcock is
Not directly boiler-related, but worth doing in preparation for winter: make sure every adult in the house knows where the main stopcock is. If a pipe freezes and bursts, being able to shut off the water immediately limits the damage.
Based in Hemel Hempstead, Ealing, or NW London and want the boiler checked before winter? Get in touch — we'll book you in while there's still availability.