What is a common feature of unions used in fire pump sensing lines?

A common feature of unions used in fire pump sensing lines is that they provide a means for easy maintenance. Unions allow for the quick disconnection of piping without the need for cutting or extensive disassembly, which is particularly beneficial when servicing or replacing components in the sensing line. This design simplifies the maintenance process, reduces downtime, and ensures that repairs can be conducted efficiently.

While other features, such as preventing leaks or eliminating the need for flanges, may be considerations in system design, the primary and most direct reason for using unions is to facilitate maintenance accessibility and efficiency.