A steam gauge pigtail is a length of tubing with one or more loops in it used to connect the steam gauge to the boiler. It functions as a protective device by preventing live boiler steam from coming into contact with the working parts of the gauge. The steam is denied passage by condensation, which forms in the loop (or loops) of the pigtail. It is recommended that the steam gauge pigtail be filled with water before it is attached to the boiler. It should be attached to the boiler in a position where heat and vibration will be at a minimum.