How to Bleed a Radiator

If you can feel that your radiator is cold at the top and significantly warmer towards the bottom, it will need to be ‘bled’ to release the air that has entered.  This will happen quite naturally over time as water enters the central heating system and is very difficult to prevent.  The air that has leaked will then distribute at the highest part of the radiator, leaving that much cooler than the bottom.

Firstly, it is advisable to switch off the central heating system so more air cannot escape into the radiator.  Each radiator has a valve on the end of the top, with a square shaft in the middle.  This needs to be gently extracted with a radiator key.  These can be cheaply acquired from a DIY store, although specific shaft designs can be removed with a screwdriver.

The idea is to slowly release the shaft until the air begins to bleed out.  This should be evident by touching the radiator to feel a rise in temperature of the higher part.  There is no need to remove the shaft completely or take the key (or screwdriver) out of the valve.  As soon as water starts trickling out of the valve, re-tighten it and the process should be complete.  It may be an idea to have a cup or other item handy to catch any falling water in case it flows faster than expected.

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