Brass Clock Radiator Key

The brass clock radiator key is the small key used to open the bleed vent on a radiator. It has a square socket that fits the common vent spindle, with a flat top to grip between your fingers, much like an old clock key.

Using the brass clock radiator key

Air in the rad makes it cold at the top and noisy. Bleeding it out with the key brings it back to full heat. Being brass, the key is solid enough to turn a stiff vent without twisting.

Switch the heating off and let the rad cool slightly. Hold a cloth under the vent, fit the key and turn it slowly anticlockwise until air hisses out. Shut it again the moment water shows. A quarter turn is usually plenty.

Afterwards, check the pressure on a combi or sealed system and top up through the filling loop if it has dropped.

Keys and other radiator bits are in our Flexible range.

Radiator keys at our Glasgow shop

Drop by Plumb Parts, 555 South Street, Glasgow G14 0QX at the counter, open Mon-Fri 8am-5pm and Sat-Sun 8am-1pm, or order online.

Specification

• Material: Brass
• Suitable for: Opening the bleed vent on radiators with a square vent spindle

Common Questions

Will this key fit my radiators?

It fits the common square bleed spindle found on most panel radiators. A few vents use a slot for a flat screwdriver instead, so take a look before you start.

How far should I open the vent?

A quarter turn is usually enough. Let the air hiss out and close the vent as soon as water starts to appear.

Why has my boiler pressure dropped after bleeding?

Letting air out lowers the pressure on a sealed system. Top it back up through the filling loop to the level the boiler maker gives.