The worst time to find out your heating has a problem is the first cold evening of the year, because that is the evening everyone else finds out too.
Heating engineers’ diaries fill up quickly once the weather turns, and a fault that would have been a routine visit in September becomes a wait in October. Most of what goes wrong at the start of the season is minor and easy to catch early. It just needs the heating to be switched on before you are relying on it.
Key Takeaways
- Run the heating now, while getting an engineer out is still easy
- A faint smell of dust and some gurgling on the first run are normal
- Check the pressure, and check it again after bleeding any radiators
- Radiator valves can stick after a summer of sitting still
- Test your carbon monoxide alarm and check its expiry date
- Book the annual service before the autumn rush, not during it
Why the Heating Side Needs Testing
If you have a combi boiler, it has been heating your hot water all summer, so it is easy to assume everything is fine. But hot water and heating use different parts of the system. The heating side, which includes the pump, the valve that switches between hot water and heating, the radiators and the thermostat, may not have run properly since spring.
Parts that sit still for months are the ones most likely to have stuck, and the only way to find out is to use them.
What Is Normal on the First Run
A few things are expected the first time the heating comes on after a long break, and none of them are a cause for concern.
- A faint smell of burning dust for the first hour or so, as dust that has settled on the radiators and inside the boiler heats up
- Some gurgling or trickling as air that has collected in the system moves around
- Ticking or clicking from the pipes as they warm up and expand
These should all settle down within a day or two.
What is not normal is a smell of gas, a loud banging or rumbling that carries on after the first run, or a boiler that keeps locking out with a fault code. If you smell gas, turn off the supply at the meter if you can, open the doors and windows, do not operate electrical switches or use a naked flame, leave the property and call the National Gas Emergency Service on 0800 111 999.
Check the Pressure
Find the pressure gauge on the front of the boiler. With the system cold, most boilers sit between 1 and 1.5 bar, although your boiler manual will give the exact figure for your model.
If it is well below that, the boiler may refuse to fire at all. Topping it up is usually straightforward using the filling loop, and the manual will show you how. If you find yourself topping it up regularly, water is leaving the system somewhere, and our post on why a boiler keeps losing pressure is worth a read.
Bleed Any Radiator That Is Cold at the Top
Once the heating has been on for twenty minutes or so, go round and feel each radiator.
A radiator that is warm at the bottom but cold at the top has air trapped in it. To bleed it, turn the heating off and let the radiators cool, then use a radiator key to open the small valve at the top corner, with a cloth held underneath. You will hear air hiss out. Close the valve as soon as water starts to appear.
Bleeding lets out a little water along with the air, so check the pressure gauge again afterwards and top it up if it has dropped.
A radiator that is warm at the top but cold at the bottom is a different problem. That usually points to sludge settled in the bottom of the radiator, which bleeding will not fix. We have written about whether a power flush is worth it if several of your radiators are behaving this way.
Free Up Any Stuck Radiator Valves
This one catches a lot of people out in the autumn.
The thermostatic valves on most radiators, the ones with a numbered head, work by pushing a small pin in and out. If a valve has sat turned down all summer, that pin can stick in the closed position, and the radiator stays cold however high you turn the heating up.
If a radiator is completely cold while the others are warm, turn the valve head to its highest setting and give the heating time to reach it. If it is still cold, the pin may be stuck. On many valves you can unscrew the head and gently press the pin a few times to free it. If you are not comfortable doing that, leave it for an engineer rather than forcing anything.
Get the Timer and Thermostat Ready
- Check the batteries in any wireless thermostat or programmer. They have often run down over the summer without anyone noticing.
- Look at your heating schedule. The times that suited you in spring may not suit the colder months.
- The clocks go back on Sunday 25 October 2026. Most smart and digital controls adjust themselves, but older timers with mechanical dials do not, and your heating will come on an hour out until you change them.
Test Your Carbon Monoxide Alarm
Press the test button and make sure it sounds. Carbon monoxide alarms also have a limited working life, so check the replace by date printed on the back.
The NHS advises having an alarm in each room that contains an appliance burning gas, oil, coal or wood. Carbon monoxide has no smell or colour, so an alarm is the only reliable warning. The early symptoms of carbon monoxide poisoning include headaches, dizziness, feeling sick, tiredness and confusion, and shortness of breath. Symptoms that ease when you leave the house and return when you come back are a particular warning sign.
If your alarm sounds, get everyone outside, leave the door open behind you, and call 0800 111 999.
Book the Service Before the Rush
An annual boiler service is the single most effective way to avoid a breakdown in the middle of winter, and September is the easiest month to get one booked. It is also what catches the problems that build up slowly, like sludge in the system or a component starting to wear, before they stop the boiler altogether. We have explained what a boiler service includes in a separate post.
If your boiler is still under a manufacturer warranty, the annual service usually matters for another reason too: most warranties stay valid only while the boiler is serviced every year. Luke’s new boiler in Cove came with a twelve year warranty, and the annual servicing was arranged as part of the job so it would never lapse by accident.
When to Call an Engineer
Some things are worth handing over rather than working around.
- The boiler will not fire, or keeps locking out after a reset. Our post on why a boiler keeps turning itself off covers the common causes.
- The pressure keeps dropping after you have topped it up
- Radiators stay cold after bleeding and after checking the valves
- The flame looks yellow or orange instead of blue, on a boiler where you can see it
- Soot or brown staining appears on or around the boiler
- The pilot light keeps going out on an older boiler
The last three can be signs of incomplete combustion, which is when carbon monoxide is produced. Stop using the appliance and get it checked.
What Not to Do
Do not remove the boiler casing or try to adjust anything inside it. Working on gas appliances without Gas Safe registration is illegal as well as dangerous.
Do not keep resetting a boiler that locks out repeatedly. The reset clears the fault code, not the fault.
Do not block the boiler’s vents or flue, or stack things against it, however tempting a cupboard full of boiler is as storage space.
Getting It Sorted
Most start of season problems are small ones, and the earlier they are found the easier they are to fix. If the checks above have turned something up, or you would simply rather have the system looked over before winter, get in touch.
We cover Reading and the surrounding area, including Wokingham, Bracknell, Crowthorne and Farnborough, for boiler repairs and servicing.