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As you heat water up to releases the air trapped within it. In the meantime the general corrosion within the system is releasing a variety of gases. The easiest way to tell if this is happening is to feel the radiator, if it is hot at the bottom but cold at the top then it is almost certainly filled with air and needs bleeding. The first task is to find the bleed valves. These are always towards the very top of the radiator and can be either side. There usually fairly obvious but can be located behind the back of the radiator and hidden from view, behind a plastic cover. Most heated towel rails have the bleed valve at the top. A double panel radiator will often have two bleed valves, one for each panel. Pentonville Plumbers bleed systems after a repair.

Tools and materials:

a). Bleed Key

b). Tissue paper.


The water that comes out of a radiator can be very dirty, so hold the piece of tissue under the valve. Turn the key anticlockwise to open the valve. Only turn the valve a few turns and don’t remove it altogether. You’ll hear the escaping from the valve. Hoxton Plumbers are experienced in bleeding the radiators in a central heating system. As the water reaches the top of the radiator this will turn into a series of wet splutters. This is the time to close the valve, whilst at the same time catching the excess water in your tissue paper. If you have a sealed system will need to recharge it, in other words getting back to working pressure (usually 1bar). If you have a gravity system is nothing else for you to do except have a cup of tea in front of a nice hot radiator.
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