Radiator Allen Key

A radiator Allen key is a small hex key used on radiators whose vents or plugs have a hexagon socket rather than the usual square spindle. If the standard square bleed key will not fit your rad, this is often the tool you need.

When you need a radiator Allen key

Some designer, column and towel radiators use a hex-headed bleed screw. A square key just spins in them. The Allen key slots into the socket and gives you enough grip to crack it open. It is also handy for hex blanking plugs on certain rads.

• Hex key for radiator vents and plugs
• Fits rads where a square bleed key will not
• Small and easy to carry
• Useful for both trades and householders

To bleed, turn the heating off first and let the rad cool a bit. Hold a cloth under the vent and turn the key slowly anticlockwise until you hear air hiss. Close it as soon as water appears. On a sealed system, check the boiler pressure afterwards and top it up if needed.

Hex sizes vary between radiator makers, so look at the old vent before you buy. If you are not sure, bring the rad’s details or a photo of the vent to the counter.

Keys, vents and radiator plugs are listed in our radiators and accessories pages.

Specification

• Suitable for: Radiator vents and plugs with a hexagon socket

Common Questions

How do I know if my radiator needs an Allen key?

Look at the bleed screw. A small six-sided hole needs a hex key, while a square pin takes a normal radiator key.

What size Allen key fits a radiator bleed screw?

It varies from maker to maker, so there is no single answer. Check the radiator maker’s details or try the key on the vent before you need it in a hurry.

Can I use a normal Allen key from a tool set?

If the size matches, yes. A dedicated radiator key is simply easier to keep with the heating bits, so it is there when the rad needs bleeding.

Getting a radiator key in Glasgow

It is at the trade counter, Plumb Parts, 555 South Street, Glasgow G14 0QX, open Mon-Fri 8am-5pm with Sat-Sun 8am-1pm at the weekend. Or buy online.