How to Bleed Radiators

How to Bleed a Radiator?

February 2, 2022 4:27 pm
Published by: smartcover

What does bleeding your radiator mean?

Air pockets may occur due to the build-up of air leading to a lower volume of water in the radiator. These air pockets reduce the efficiency of the radiator and can be eliminated by bleeding your radiators.

Note that bleeding your radiators is not the same as flushing or draining your central heating system.

If your heating problems aren’t fixed by bleeding your radiators, then your radiators might need draining/flushing. Flushing removes the build-up of magnetite (dissolved metal that deposits in the form of a black sludge in the radiators) from your heating system. It is recommended that flushing is completed by a professional.

Fortunately, bleeding your radiators only takes a few seconds and is easy to do.


When to bleed radiators?

Here are a few signs that might indicate to you that it’s time to bleed your radiator:

Radiator cold at the top:

This is one of the most common signs that your radiator needs bleeding. The radiator becomes cold at the top due to an air blockage that stops the flow of hot water from circulating throughout. Your radiator can heat up effectively only if that airlock is released.

Entire radiator is cold:

This is not a very common sign that signals air traps in radiators but is a sign that your radiator needs attention. This might be caused due to any air trap in the pipes that has restricted the flow of hot water into the radiator from the pipe. This can result in bigger problems later on if not sorted out soon. Get in touch with a local heating engineer to quickly fix this issue.

Contact a heating engineer near you.

Damp patches around the house:

Remember noticing any damp patches or mould appearing on the walls, particularly in rooms that you don’t use so often? If yes, then your radiators need some attention.

Rattling noise:

You might hear some funny noises like gulping / gurgling or rattling from your radiators due to trapped air in the heating system. This could be due to many other reasons and may signify that your radiator needs bleeding.


Steps To Bleed Radiators:

To bleed radiators, follow these steps one by one:

  1. Turn on heating: Turn your heating on and give it some time until all the radiators in your home warm up (time taken depends on the number of radiators you have and the size of your house.)
  2. Identify the radiators that need bleeding: Check the radiators one by one to ensure that each one of them has an even temperature across the whole surface area. If you find any radiator/ radiators giving out funny noises or feeling cold at the top and hot at the bottom, then it is a good signal that you need to bleed your radiator. (Tip: Wear a thin pair of gloves while checking each radiator as they tend to be very hot)
  3. Turn off heating and allow radiators to cool: Before starting to bleed your radiators, we suggest you turn off your heating so that the radiators wouldn’t be too hot to touch.
  4. Place a cloth beneath the radiator bleed valve: Identity the radiator bleed valve and make sure that you place a cloth or an old towel to catch any water that may drip or release. (Tip: Bleed valves are located at the top corner of a radiator and look like a round hole with a square inside.)
  5. Open the valve & release the air: Even after opening the valve to release the air, you find no water or air coming out, then the chances are that the valve could be blocked with paint. Close the inlet and outlet valves at each end of the radiator and slowly remove the screw from the bleed valve’s centre point. Now insert the radiator key into the bleed valve and slowly turn it in the anti-clockwise direction, just a bit. If you hear any hissing sound, it means that the air is escaping through it. (Tip: We suggest you have a bucket handy to hold any leaking water, just in case the valve gets opened to an extent too far.)
  6. Close the Valve: Once the hissing sound stops and water starts to leak, immediately turn the key clockwise to close the valve.
  7. Check Boiler Pressure: Repeat the same process for each radiator to bleed. Once this is done, you need to check the pressure of your boiler’s water pressure gauge.

How to bleed radiators without key:

Bleeding your radiator without a key might sound complex, but the truth is that it is not. This is because there are many things that you can use instead of a radiator key.

Here below, you may find some best alternatives for radiator bleeding key, which would do just as good as a key would. However, before we reveal what these alternatives are, there are some tools that you shouldn’t be using for this job.

For instance, you should avoid using pliers. Some people tend to think that this would be a good option as they can get the screw in a grip quickly so that releasing the air by opening the valve also gets easier. However, the fact is that pliers can easily damage the screw, making it difficult to close the valve or bleed the radiators again.

It would be good to avoid using a cross-head screwdriver as it will scratch/damage the valve. Instead, you could use the following;


A flathead screwdriver:

If the bleed plug in your radiator has a small slit in the middle, you can use a flathead screwdriver to open it. However, not all radiators will have a slotted screw, so this type of tool may not be suitable for all radiators.


Steps to bleed a radiator without key:

  1. Turn off heating: Turning off heating will reduce the water temperature in radiators. This would prevent you from burning yourself.
  2. With a cloth in hand, put the screwdriver to the slotted groove and turn it in the anti-clockwise direction. Catch any water that sprays out. A hissing sound would be heard as the airlock releases.
  3. Once the hissing sound has stopped, re-tighten the valve to prevent the water from escaping the radiator.
  4. Turn the heating back on.
  5. Check the pressure gauge on the boiler and top it up if low.
  6. Leave the radiators to heat up for an hour and check if the heat is evenly spread throughout them.

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