If the bottom of your central heating radiator is warm but the top is cold it means that the radiatorradiator bleeding image is malfunctioning and needs bleeding. Remember to take care and not burn your hand on the radiator when you are checking this. Bleeding is not a medical process but it is a way of getting care and of the radiator so that the hot water can properly flow through the radiator keep it warm and able to your property.

If the whole radiator is cool radiator despite the fact that the central heating system is on then it could be that the radiator is almost full of air. The air prevents the hot water circulating and no real difference in temperature between the top and bottom of the radiator will be experienced. This problem will contrast with the remainder of the other radiators in your central heating system which will be hot to the touch if they are operating normally.

How do I bleed a radiator at home?

The process for bleeding a home radiator is relatively simple and safe if you follow a few procedures. All radiators are supplied with a small bleed key. If you don’t have one they can be obtained cheaply from a local diy shop. Look carefully near the top of the radiator and on one side you should see a small protrusion called the bleed valve. To bleed the radiator you need to open this bleed valve a small amount. When you do this listed carefully and you will hear the air escape from the top of the radiator. Ensure that you do not allow the water to flow out as it could scald you or mark the carpets. Pay attention because at some point the air will have been fully expelled and will be followed by hot water. At this moment you need to be able to switch the valve off without delay.

If you decide you want to bleed a radiator in a sealed system you will first need to reduce the air pressure in the whole system (consult your manual for how to do this). Do remember that when you have finished you will need to top up the system afterward from the main cold water feed.

BE CAREFUL when turning the bleed valve. Have a small plastic bowl to catch any drops of water which escape and an old rag to shield your hand if required.

bleed radiator imageFirst switch off the heating boiler, failure to do this could allow more air to get into your system. Use the radiator bleed key to carefully turn the bleed valve counter-clockwise a small amount, 1/2 turn would be ample here. The air trapped in the radiator will start escaping with the hissing sound we mentioned – it is similar to a that in a bicycle tire. when you start to pump it up. When finally water begins to drip out of the valve you will know that all the air has been purged, and you can now carefully gently twist the bleed valve the other way to close it. Check for any leaks and then switch the heating back on and thoroughly check that there are no ongoing leaks from the radiator valve you have just bled. If there are check that you tightened it properly.

As we covered earlier check the system pressure and top up the water f the central heating system was a sealed system, if you have any problems consult your central heating system manual.

If you have followed the radiator bleeding process as outlined and it not seem to improve the operating performance of your heating, especially if several central heating radiators are malfunctioning, there may be another problem and you will need to call out a plumber.

How much do replacement radiators cost?

If you are searching for replacement radiators they can be purchased direct from suppliers for installation by a trained CORGI engineer. Some examples are illustrated below.

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6 Responses to “Bleed a Radiator”

  • Mary Legworth says:

    I thought that this would be difficult but, thanks to your article, I managed to complete it and my lounge radiator is now warm all over. A great help and thanks.

  • Brian T says:

    When I did this all was good when the air was coming out then the water that followed was brown. Does this show I have a problem?

  • Boiler Systems says:

    Not always. Often water in heating systems is discoloured from some internal rust or from inhibitor chemicals which may have been added at installation.

    If your system is old ask the heating engineer for a second opinion at the next service.

  • Leonne Walt says:

    Really helpful. My mum lives 100 miles away and had a problem with her bedroom radiator. I emailed this link to her and it gave her the confidence to bleed the radiator herself.

  • carlos russi says:

    DEar Sirs , I have boght a flat in south london . We have a Worcester Bosch 240 Combi RSF Boiler. We Had pay a bout £400 in total to Global GAs , who was recomended to us by EDF ,our supplier. They got the boiler working again but they can not garantee quality of the job . Just because we dont have the manual for this type of boiler. I think it is unusual , and not good enough. I am worried that because we dont know how to set up the timer on the boiler we have to turn it on/off from the wall . Who can I go to get a manual for this boiler. An get a secon look by a professional but this time with the correct manual so we can be sure that our heating system is working properly and not using unnecessary energy.


    Carlos Russi

  • Boiler Systems says:

    You should be able to get a manual from the manufacturer. Worcester Bosch after sales can be contacted on 08457 256206. Their literature line is on 01905 752556.

    If you want npower to review the heating you can call them for a quote. You can also discuss taking out an annual boiler maintenance agreement rather than taking a one off visit which may be more economical for you.

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