How to bleed a radiator – New home maintenance 101

Sep 21, 2022 | Articles, Electricity & Gas, Moving Guides

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Most properties in the UK are heated by radiators in each room, filled with hot water by a central boiler. With the rising cost of gas, you’ll want to make sure your heating is as efficient as possible. That’s why it’s important to know how to bleed a radiator, as well as when you should check your radiators and what tools you’ll need for the job.


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Why would I bleed a radiator?

While the name sounds dramatic, bleeding a radiator just means releasing trapped air. Bubbles of air in your radiators prevent your radiators from heating completely, meaning they aren’t as effective at heating your home.


How can I tell if a radiator needs bleeding?

If you’re ready to check the radiators in your home, start by turning on the heater as well as the radiator in each room. To successfully bleed all of your radiators you will need to build up some pressure to force the air to the top, so your heating will need time to warm up.

Once your radiators are hot, feel along the front of each one, especially towards the top. Any cold spots indicate that there is trapped air and that the radiator needs bleeding.


What tools do I need to bleed a radiator? 

There’s only one specific tool you’ll need, but it depends on the type of valve on your radiator. The valve is a round metal panel on the side of the radiator, in the centre of which will either be a square (as in the photo below) or a flat line.

If your valve is a flat line then you can open it with any flat-headed screwdriver, but if you have a square valve you will need a radiator key – you can see one in the photo above. If there isn’t a key at your property you can buy them in any hardware store or from an online retailer for around £3.

Aside from the screwdriver and key, it’s a good idea to have an old towel or rag to hand as well as a bucket, as some water often comes out along with the trapped air.


How to bleed a radiator

Once you have your tools assembled, you’re ready to begin:


Step 1

Now you’ve found which radiators need bleeding, turn your central heating off to avoid burning yourself.

Step 2

Once the radiator has cooled, place your key or screwdriver in the slot in the valve and then press a towel or rag against the valve. Keep the bucket underneath where you are working to catch any drips.

Step 3

Carefully turn your key or screwdriver anti-clockwise to open the valve. You should hear the hissing sound of air escaping, and it will take twenty to thirty seconds to release all the air. Once the air has been let out the valve will start leaking – or spurting – water immediately, so be ready to close it quickly.

Step 4

Repeat this process for every radiator with cold spots in the home. When you’re finished, turn the heating back on and wait for your radiators to warm up again. Check again for any cold spots, and make sure that none of the valves is leaking water.



How often should I bleed my radiators?

You should bleed your radiators once a year – the end of summer is a good time in preparation for turning the heating back on in winter. You should check your radiators regularly for cold spots every month. If you find you’re bleeding your radiators more than once a year it might be an indicator of a larger problem with your heating.

Want more tips on making your heating more efficient? Visit our guide on how to save on energy bills even if your property has a low EPC


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