How does a bleed valve work?
|Radiator bleed valves have many names, including air release valve, bleeder valve and bleed nipple.|
|The purpose of the bleed valve is to release air that sometimes gets trapped inside radiators, making them less efficient.|
|The valve comprises a plug that screws into a radiator tapping at the top of the radiator, and an adjustable bleed screw, with a 5mm square head, in its centre.
The plug, which usually has a half-inch British Standard Pipe (BSP) thread, is screwed into one of the two top tappings – internally threaded holes at each corner of the radiator.
|Bleed screws on most modern radiators also have a slot in the head so that they can be loosened and tightened with a screwdriver.|
|Some plugs have external hexagonal heads that can be turned with an ordinary spanner of the right size, or an adjustable spanner.|
|Others have a square recess, also known as a square section, which is fitted or removed with the square end of some multi-purpose radiator keys.|
|Turning the bleed screw anti-clockwise with a radiator bleed key releases any air. Turning it clockwise tightens it up again.|
|For a step-by-step guide to the bleeding procedure, see:|