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How to Bleed Your Radiators - 2024 Guide

When your radiators don't seem to be heating your home as they should it is likely that they need to be bled. Bleeding your radiators helps to ensure that they are working at their optimum level and that your home is being heated efficiently.

It is important to bleed your radiators as air pockets in the system prevent hot water from circulating around the radiators, meaning the heat cannot be distributed evenly.

When Should You Bleed Your Radiators?

  • High Pressure Reading: If your boiler pressure gauge is showing higher than usual (check you boiler manual for your default pressure reading) then it could be the excess air in the rads causing it. Typically it should be around 1-1.5bar.
  • Moving house: If you have recently moved into a new property it's always a good idea to give you radiators a quick check.
  • Cold at the top: If you have noticed cold spots at the top of your radiators then this is usually a sign that air is trapped and bleeding them can help resolve the issue.
  • Noises: If your radiators are making strange noises (other than the typical sounds made with heating and cooling expansion and contraction) then it could be asymptom of air in the system.

How Often Should Radiators Be Bled?

There is no set rule for how often you should bleed your radiators. Generally it is recommended to bleed them at least once a year regardless of whether you notice any symptoms. Other than that, simply checking for the telltale signs mentioned above and bleeding when necessary is enough.

How Long Does It Take?

The time it takes to bleed a radiator can vary depending on the type of radiator you have, the air pressure in the system and any other obstructions such as radiator covers. THe actual process of bleeding a radiator however is a relatively quick and straightforward process. On average it should take no longer than a minute to bleed a single radiator and most households can be done in under 15-30 minutes.

What You Will Need:

  • A radiator key – This is a special tool used to open the bleed valve on your radiator. It will have a triangular recess which matches the valve.
  • A bucket or tray – This will be used to catch any water that comes out of the radiator when you bleed it.
  • A cloth – This will be used to wipe away any excess water around the bleed valve.
  • A pair of gloves – Though you shouldn't bleed a radiator when hot you may want to consider wearing some gloves.

What's the Process? A Step-by-Step Guide

Before starting the process it can pay to identify which radiators need attention. This can be done simply by turning on your heating and visiting each radiator feeling for a cold-spot at the top. Once identified, and the radiators cooled you can proceed with the steps below:

  1. Place a bowl or bucket beneath the bleed valve. To catch any water that might come out of the bleed valve during bleeding place a bowl or bucket beneath it. This will help keep mess to a minimum and prevent damage to floors and carpets.
  2. Use a radiator key to open the bleed valve. Using a radiator key (which is typically available at any DIY store) gently turn the bleed valve about a quarter turn anti-clockwise until it opens. A hissing sound will indicate that air is escaping from the system as it is replaced by water from the main supply line.
  3. Close the bleed valve when water appears. Once you can see that water has replaced all of the air in the system (and is now trickling out the valve) close the bleed valve by turning it clockwise until it is firmly closed.
  4. Check your boiler pressure. If your pressure gauge was unusually high beforehand, you may now notice it has settled to a more acceptable level.

It's now as simple as repeating these steps for every radiator identified as having air in it. Once complete you can check your boiler pressure. If your pressure gauge was unusually high beforehand you may now notice it has settled to a more acceptable level.

A Word of Caution

Burns: Though it is tempting to proceed while the rads are still hot you do run the risk of scalding yourself when water eventually releases from the valve.

Leaks: It's worth double-checking you have tightened up the bleed valve sufficiently to stop the escape of water. They don't need to be over-tightened, and it often feels as though they aren't closed when the key comes to an abrupt stop.

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