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How To: Bleed a Radiator

Over time, air pockets can build up inside of your heating system and can cause cold spots at the top of your radiator(s).

It can come at great cost, if you have air pockets and sludge building up in your radiators, as you're still paying your bill, but not getting the heat from your system.

Here’s how you can bleed your radiators

Step One

Turn your heating system on, so that the system will create pressure and push the air pockets around, and eventually out.

Step Two

Inspect all of the radiators in your system, and see which ones need to be bled. This can be done by feeling for cold spots at the tops of each radiator, or if you can hear a flowing or gurgling sound.

Step Three

After you have identified which radiators need to be bled, turn off your central heating. This will ensure that you will not scald yourself with hot water, and you will not spill water everywhere!

Step Four

Lay down some precautions, as this can be a messy job! Old towels and rags should be laid around the radiator(s) being bled, and you should have a bowl/container for any excess water to flow into.

Step Five 

Open the bleed valve using the bleed key, turn this between a quarter and a half turn, this way, you won’t see any excess water flowing out. The indicator of air escaping from the radiator is a hissing sound, this air may be hot, so please take precautions.

Step Six

As mentioned in step five, ensure that you only turn the key between a quarter and half turn, as if it goes any further than this, water will come rushing out of the radiator. Allow the hissing sound to run its course, then when it stops and you see water dripping from the system, then you can turn the valve back to its original position. DO NOT OVERTIGHTEN.

Step Seven

Carry the bleed out for all of the radiators in your system.

Step Eight


When you bleed your heating system, you almost always lose some water, if there is a large loss, your central heating may have issues.

You will need to check the pressure of your heating system, which you can do by looking at the gauge on your boiler. If it is pointing to green, no action is needed, but if it is pointing to yellow or below, you must repressurise the system. This is done via the central filling loop.

More information on this can be found in our other blog posts!

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