Which component is used to connect two pipe sections and allow disassembly for maintenance without leaking?

• A. Mainline isolation valve
• B. Drain valve
• C. Sleeving
• D. Unions

Answer: (D)

Unions are fittings designed to join two pipe sections with a removable joint. They consist of two connection halves held together by a central nut and a gasket. When the nut is tightened, the gasket is compressed and the faces are pressed together, creating a leak-tight seal while the pipe remains continuous. The key advantage is that the two halves can be separated simply by loosening the nut, allowing maintenance or replacement of downstream components without cutting or disturbing the rest of the system.

This isn’t about stopping flow or draining a line, which is what a mainline isolation valve and a drain valve are for, respectively. Sleeving is a repair method used for damaged pipe that doesn’t provide a detachable joint for routine disassembly. So the component that best fits the idea of connecting two pipe sections and enabling easy disassembly without leaks is the union.