What is a bleed key?
The parts of a bleed key are:
Bleed keys are used for 'bleeding', which is the release of air from radiators via the air vent plug. Air trapped in a radiator can drastically reduce its efficiency.
They are known as air release keys, bleed keys and air vent keys.
Bleed keys are for loosening and tightening the square headed bleed screw located in the middle of the bleed plug at either the top left or top right of a radiator. Some also have a slot in them for a screwdriver, like this one, but a bleed key is less likely to damage the bleed screw.
Seefor a step-by-step guide to this procedure.
Some bleed keys are sold 'carded' - that is, they are laminated to a printed card and may be sold in multiples of two or more.
Bleed keys can be made from brass, zinc-plated brass, nickel-plated iron, copper, aluminium, zinc-plated steel or alloys, which are mixtures of two of more metals. These metals or coatings are used because they will not rust.
Some bleed keys are shaped like clock keys.
Others follow a simple 'T' design.
Some bleed keys have a long wire handle for a particular reason...
...Some older radiators have their air vent plugs inserted into the back of the panel and are difficult to turn with a normal key. The rear access key makes the job much easier.
At the critical stage of bleeding a radiator, water squirts out, which can sometimes be a bit messy even if you use a cloth to try to catch it.
There are keys that include a bottle to catch the water, so there is never any mess.
You might think a cheap alloy key isn't as good as a more expensive one. However, it does have an advantage.
Because the key's metal is softer than the bleed screw, it is less likely to damage the bleed screw head than harder keys.
One of the most common things to go wrong with radiators is damage to a bleed screw. If the screw's square edges get worn, it might become impossible to turn it.
For a step-by-step guide to using these keys, see: