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Bleeding radiators: What to do – and why you should do it


bleeding radiator

When you bleed your radiators, you release any air that is trapped inside them. It is hard to prevent air occasionally making its way into your radiators, and it is important to remove it because not only can it cause irritating noises, but it also reduces the efficiency of your heating system.


Why is it important to bleed radiators?

It is important for you, your wallet and the Earth’s resources.

Improve efficiency: When air is trapped in a radiator, it can prevent the hot water circulating to all parts of the radiator, thus reducing its efficiency. By bleeding a radiator, you can ensure that it operates at full capacity.

Save money and energy: Inefficient radiators have to work harder to heat a room. This means that they consume more energy than they should. By bleeding your radiators, you can save energy – which has a beneficial effect on your heating bills.

Reduce noise and banging: Have you ever heard banging noises coming from your radiator? Air trapped in a radiator can cause knocking or banging noises. Bleeding your radiator can help eliminate these noises. If the banging noises continue after you have bled your radiator, have a look at our radiator guide here. It contains a number of suggestions for why a radiator may be making strange noises.


How to bleed radiators

It is really easy to bleed our radiators. You do not need a radiator key or any special tools – all you have to do is turn the bleeder valve. If it is a little tight, you can loosen it with a standard pipe wrench or an adjustable spanner. Otherwise, bleed the radiator as described below.


Bleeding radiators – a step-by-step guide:

  1. Switch off the circulation pump or the heating system; allow time for the radiator to cool down if the supply temperature of your heating water is high. This is to make sure you don’t burn yourself on your radiator. In addition, the system will continue to transport the air bubbles around if you leave the circulation pump running. This will make it harder to bleed your radiators correctly.
  2. Locate the bleeder valve on your radiator. It is a small white knob, often to be found on the top of the radiator. Turn it counter-clockwise.
  3. Place a bowl or a cloth under the bleeder valve to catch any water that may seep out.
  4. Turn the bleeder valve slowly until you hear a hissing noise. This is the sound of the air escaping.
  5. As soon as water starts to seep out, retighten the bleeder valve. When water seeps out, this indicates that all the trapped air has been released. If no water seeps out, you need to top up the heating system.
  6. Don’t forget to restart the circulation pump or the heating system once you have finished.


How often should I bleed my radiators?

Generally speaking, you should bleed your radiators at least once a year. The best time to do so is typically at the start of the heating season, i.e. just before you start using your radiators regularly. In autumn, in other words.

However, the timing may vary depending on your specific heating system and the conditions it operates under. Here are some scenarios where you may need to bleed your radiators more often:

  • Your radiators are on, but cold in places: Do your radiators feel cold in places, even though they are on? This may indicate that there is some air trapped inside. Another indication is that your radiators are not heating efficiently.
  • You can hear noises: If you hear knocking or banging noises from your radiators.
  • You have just adjusted your heating system, or have recently replaced some parts: When you perform maintenance on your heating – refilling it with water, for example – this may result in air becoming trapped in the system.


How long does it take to bleed radiators?

The process of bleeding a radiator normally takes just a few minutes. However, most people have several radiators in their homes and you will have to repeat the process for each and every radiator. This means that the entire process can take between 30 minutes and a couple of hours, depending on how many radiators you have and how much air is trapped in them.

Similarly, once you have bled your heating system, it may need to be refilled with water to maintain the correct pressure, and this will naturally take a little more time.


Can I have someone do this for me? And who should I contact if I have any problems?

If you don’t feel comfortable bleeding your radiators yourself, or if you have any problems with the process, you can always hire a professional to do it for you.

Contact your local plumber or a heating technician. Both have the necessary knowledge and experience to handle the assignment safely and efficiently. They can also help resolve any issues you may be having with your heating system.

If your radiators still contain air after they have been bled, or if they still fail to heat correctly, this may indicate a more serious problem with your heating system. A professional will be able to determine what the problem is – and then deal with it.


Is the process the same, regardless of what type of radiator I have, and how old it is?

Generally speaking, the process of bleeding radiators is largely the same, no matter what type of radiator you have. You need to locate the bleeder valve, carefully open it to allow the air to escape and then retighten it when water starts to seep out.

That said, there may be some small differences, depending on the specific properties of your radiators:

  • Type of radiator: Some modern radiators are fitted with automatic bleeder valves. These are designed to release trapped air automatically, which means that there is no need to bleed them manually. Check your radiators to see if they feature this function.
  • Layout of the heating system: Some systems, especially those that run across multiple storeys, may require you to bleed the radiators in a specific order, normally from the bottom up. This ensures that any trapped air can rise up and out of the system.
  • Age and condition of the radiator: Old radiators may have a tendency to develop problems such as corrosion, which may influence the bleeding process. In addition, the bleeder valves on old radiators may be harder to loosen. If the valve is stuck, try using a wrench. If this still doesn’t work, apply a little lubricant rather than simply using more force, which risks damaging the screw. Otherwise, you may need to seek professional assistance.


If you have any doubts:

Generally speaking, if your radiators are old and/or corroded, it is best to call in a professional to take care of the maintenance and bleeding. This should ensure that the work is done safely and efficiently. Otherwise, it is always a good idea to read the instruction manual for your specific radiators and heating system.

Finally, it is absolutely worth considering replacing any old, corroded radiators with new models. This is often the key to improved efficiency and less maintenance.

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