How to prepare your heating system for winter: boiler, radiators and chimney

To prepare your heating for winter, do four things before the first cold spell: book the annual service of your boiler or gas heater, bleed the radiators, have the chimney or flue swept if you burn anything, and test your smoke and carbon monoxide alarms. Only the radiators are a safe do-it-yourself job; the rest involve gas, combustion or flues and should be done by a qualified professional. The order below is the one that avoids the autumn rush and a cold surprise in December.

Seasons depend on where you live. In the southern hemisphere, read "autumn" as March to May and do this in the months before your own winter.

Week 1: book the professionals first

Technicians fill up as soon as the weather turns, so make the calls early.

• Boiler or gas heater service. An annual check by a qualified engineer looks at combustion, the flue, the safety devices and the gas connections. It is the single most useful heating task, because it protects against carbon monoxide as well as breakdowns. In some countries the annual service is a legal requirement, and in many it is required for rented homes. Check what applies to you.
• Chimney or flue sweep. If you have a wood stove, an open fireplace or a flue that serves a boiler, soot and nests build up and can block the exit of fumes or catch fire. A sweep once a year before the season is the normal rhythm, and in some places the frequency is set by regulation depending on the fuel. Ask the sweep for a certificate if your insurer or landlord may want it.

Never open a gas appliance, adjust a burner or disassemble a flue yourself.

Week 2: bleed the radiators

Air trapped in a hot-water radiator keeps the top cold while the bottom is warm, and the room never heats evenly. Bleeding takes about five minutes per radiator.

1. Turn the heating on and let the radiators warm up, then find the cold ones or ones that are cold at the top.
2. Turn the heating off and wait for the system to stop circulating.
3. Put a cloth under the bleed valve, open it slowly with the bleed key and listen for the hiss of air.
4. Close the valve as soon as water starts to come out.
5. Check the boiler pressure gauge afterwards. Bleeding can lower it, and the manual of your boiler tells you the right range and how to top it up. If you are not sure, ask the installer.

Do this once a year, at the start of the heating season (the related hot water routine is on the water heater page). If you must bleed the same radiator again and again, there is a leak or a fault in the system: call a heating engineer. Not every system has bleed valves: electric radiators and underfloor systems do not.

Week 3: simple checks around the house

• Clear the area around radiators and vents. Furniture, curtains and clothes stop heat reaching the room, and anything touching a heater is a fire risk.
• Check for draughts. A lit candle or a stick of incense held near window and door edges shows where air moves. Weatherstripping is a cheap, simple fix.
• Dust the radiators and convectors. Dust burns and smells the first time they come on.

Week 4: test the alarms

Anything that burns fuel can leak carbon monoxide, which has no smell. Press the test button on every smoke and CO alarm, replace the batteries that are due and check that the CO alarm is near the sleeping areas (see how to run the full safety check). If a CO alarm sounds, go outside into fresh air and call the emergency services or your gas company.

What not to do

• Do not use a gas oven, a barbecue or a camping stove to heat a room.
• Do not block air vents that feed a boiler or a stove.
• Do not ignore a yellow or orange flame on a gas burner that should be blue, black soot marks around the appliance, or a pilot light that keeps going out: stop using it and call a professional.

Put it on the calendar

These jobs come once a year, in the same order, at the moment of the year when it is easiest to forget them. HouseKiper schedules the heating service, radiators and chimney with the rest of your seasonal tasks and reminds you when it is time. You can see the full list in the fall checklist and the winter checklist.

When should I service my boiler?

Once a year, ideally in late summer or autumn, before the heating season starts, when technicians have more availability. In some countries it is a legal requirement.

How do I know my radiators need bleeding?

If a radiator is cold at the top and warm at the bottom, or gurgles, there is air trapped inside. Bleeding it with a radiator key usually fixes it in a few minutes.

Can I sweep my own chimney?

It is not recommended for most people. A professional sweep checks the flue for damage and blockages and, where required by regulation or your insurer, issues a certificate.

Is it normal for the heating to smell the first time I use it?

A light smell of burning dust is common and fades quickly. A smell of gas, soot or burning that persists is not normal: switch the appliance off, ventilate and call a professional.