A union is a threaded fitting which allows the pipe work to be separated and reconnected without any horizontal movement in the pipe. It can be a standalone pipe fitting connecting two pieces of pipe, or an integral part of another fitting (such as a ball valve) which allows it to be separated.

A union is a threaded fitting which allows the pipe work to be separated and reconnected without any horizontal movement in the pipe. It can be a standalone pipe fitting connecting two pieces of pipe, or an integral part of another fitting (such as a ball valve) which allows it to be separated.