How do I get a heating system ready for winter?

Heating systems fail on the first genuinely cold night, which is precisely when every engineer is busy and call-out rates are highest. Testing it in September gives you weeks to fix whatever shows up.

Safety

Step by step

1. Run the system for an hour on a mild day.Turn the thermostat up and let everything come on. Most faults reveal themselves within the first hour, and finding them now is a booked appointment rather than an emergency.
2. Check the boiler pressure.The gauge should sit in the marked band, typically around 1 to 1.5 bar when cold. Low pressure is the commonest single fault and is usually repressurised in a couple of minutes. If it drops repeatedly, there is a leak.
3. Feel every radiator top and bottom.Cold at the top means trapped air and needs bleeding. Cold at the bottom with a hot top means sludge, which is a different problem and needs flushing rather than bleeding.
4. Bleed the ones that need it.Heating off and cool, key on the valve at the top corner, cloth underneath, open until water comes instead of air, then close. Work upwards through the house, and check the boiler pressure afterwards — bleeding drops it.
5. Exercise every radiator valve.Valves seize shut over summer. Turn each fully open and closed a few times. If a thermostatic valve head spins with no effect, the pin underneath is stuck — pull the head off and free the pin gently.
6. Set the thermostatic valves for the season.Rooms you use warmer, spare rooms and hallways lower. This is where most of the saving is, and it is easier to do now than when the house is already cold.
7. Check and set the timer.Confirm the clock is right after the summer, and set a schedule that fits how the household actually uses the house rather than last year's.
8. Look for leaks and damp around the system.Under radiator valves, around the boiler, at the pump and near any visible pipework. Small weeps left over summer become winter failures.
9. Have the filter emptied and the boiler serviced.Book it in early autumn. A magnetic filter cleared at the service catches the sludge that would otherwise reach the heat exchanger, and many warranties require an annual service anyway.
10. Check the condensate pipe before the first frost.A plastic pipe from the boiler, often running outside. If it runs externally and is not insulated, it freezes and shuts the boiler down — insulating it in autumn is a five-minute job that prevents a very cold morning.
11. Test the carbon monoxide alarm.Press the test button, and check the expiry date on the unit. Heating season is when it matters and when it needs to be working.

Tips

• Do this in early September. By November, engineers are booked several weeks out and emergency rates apply.
• Note the boiler's normal cold pressure on a label near the gauge. Knowing what normal looks like makes an abnormal reading obvious.
• If a radiator has been cold at the bottom for years, that is sludge that has been getting worse. Deal with it before it reaches the boiler.

Common mistakes

• Waiting for cold weather to test the heating — The first cold night is when every engineer is fully booked and call-out charges peak. Nothing is gained by finding out then.
• Bleeding radiators without checking the pressure afterwards — Bleeding releases water as well as air, so system pressure drops. Repeated bleeding without repressurising eventually locks the boiler out.

If it doesn't work

Questions people ask