What is a three legged radiator key?
The parts of a three-legged key are:
The three legged radiator key is also known a 'lockshield valve key'. It is often made from brass, galvanised or zinc-coated steel or an alloy (a mixture of two or more metals) - all materials that will not rust.
Like the four-way key, it can be used on the drain-off cocks - also know as drain taps or valves - on some radiators.
For certain kinds of maintenance work, all the radiators of a system might need to be drained.
Because it is sometimes referred to as a lockshield valve key, it's easy to make the mistake of thinking it can be used on radiator lockshield valves that are covered with plastic caps. These are the valves that can be adjusted to regulate the flow of water in a procedure known as 'balancing'.
The term 'lockshield' in this case actually refers to drain-off valves that have a collar of metal around the square valve head, like this one, to prevent unintended operation.
A lockshield valve like this is also known as an 'anti-vandal' valve because it is difficult to interfere with unless you have the lockshield key that fits it.
The appropriate leg of a three-legged key fits perfectly inside the collar and over the square head.
The three-legged key has a different-sized square socket at the end of each leg to fit 1/2 inch, 3/4 inch and 1 inch radiator drain-off valves, some outside taps and some square-headed gate valves.
Unlike the four-way key, it cannot be used on water, gas and electricity cabinets.