How To Bleed A Radiator, By Greater London Properties
If a radiator is cool at the top and warm at the bottom you will need to bleed the radiator. Trapped air in the system prevents the heated water from circulating around the radiator fully and so the radiator often feels warmer at the bottom.
If the whole radiator is cold, check that the radiator valve is turned up (see diagram below). If more than one radiator is cold, the whole heating system may need to be checked by a heating engineer. Call your property manager during working hours.
Turn off the heating system before bleeding otherwise the pump might draw more air into the system. You will need a special radiator key, available from most DIY and hardware shops. You will also need a rag or cloth and a bucket or bowl.
Bleeding a radiator is a relatively simple and safe procedure. All radiators come with a ‘bleed key’(see diagram below). There will be a protrusion near the top of the radiator, on one side, called the bleed valve. You will need to open this valve a small amount to allow the air to escape from the top of the radiator whilst not allowing the water to flow out. Take care when turning the valve, have an old rag to shield your hand and a small bowl to catch any small drops of water which may escape.
First turn off the heating or you could import more air into the system. Fit the bleed key into the bleed valve and carefully turn it counterclockwise only a tiny bit, usually just a quarter or half turn. The air will start escaping with a hissing sound similar to a bicycle tire. When water begins to dribble out, all the air is purged, and you can gently return the bleed valve to its previous position. You should then remember to turn the heating back on and check that there are no leaks from the radiator valve.
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