What is a radiator spanner and air release key?

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   Parts of a radiator spanner and air release key 
 Radiator spanner and air release key 

The parts of a radiator spanner and air release key are:


  • Hexagonal ends for the installation and release of internal hexagon radiator valve tails

  • Grooves for installing and removing internally lugged valve tails

  • Square socket for releasing and tightening bleed screws

The handle can be the short or long shaft, depending on what radiator part is being adjusted.

 Radiator spanner air release key 

The handle can be smooth, like this, or the hex shape can be continued along the length of the tool.


 Grooved end of radiator spanner and air release key 

The short end of the tool doubles as a key for internal hexagon valve tails and and internally lugged valve tails by means of the grooves on opposite sides.

 Bleed key end of radiator spanner 

At the other end is a bleed key for standard 5mm square-headed bleed screws.

 Radiator spanner and air release key 

These keys are usually made from zinc-coated or galvanised mild steel or high tensile steel.


High tensile steel is the best option when removing or fitting valve tails as quite a lot of pressure might be required.


High tensile steel is much stronger than mild steel and will not distort or break easily.

 Bleeding radiator with bleed end of radiator spanner 

The combination of bleed key and valve keys is handy because you need to bleed a radiator after replacing valve tails.


For step-by-step guides to using this and some other keys, see How to bleed a radiator and How to fit and remove valve tails

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