What is a stopcock key?

  Shop for Stopcock Keys     
  Three different stopcock key heads  

Stopcock keys are devices for turning on and off water main stopcocks located in places that are often difficult to access.

  Stopcock keys for external use  

There are stopcock keys for external – outdoor – stopcocks . . . 

  Stopcock key for internal use  

. . . and for internal – indoor – stopcocks.

  Crutch stopcock key long shaft  

Many stopcock keys have long shafts so that they can reach external stopcocks that are below ground level and therefore difficult to access.

  Stopcock below ground level  

Some outdoor mains water stopcocks can be several feet deep.


Stopcock key sizes

  Stopcock and inlet-outlet pipes   

The size of a stopcock key is given in relation to the diameter of the mains pipework connected to the stopcock – in other words, the size of the stopcock’s connection to the mains. The pipework is usually measured in BSP (British Standard Pipe) sizes, which are always given as imperial measurements (inches), but each size has a metric equivalent.

  Half-inch stopcock   

The metric equivalent used is known as diametre nominale (nominal diameter), which rounds off the measurement to give a whole number rather than including any decimal points. 


The most common sizes of stopcock key fit 1/2 inch (15mm) stopcocks, like the one shown here, and 3/4 inch (20mm). There are also keys to fit 3/8, 5/8 and 1 inch (10mm, 16mm and 25mm) stopcocks.


Turning the key 

  Clockwise and anti-clockwise  

After placing the head of the key over the head of the stopcock (the visible turning part), you turn the key clockwise to turn the stopcock off and anti-clockwise to turn it back on.