Which fitting is ideal for creating a tight connection that allows for disassembly?

The union fitting is specifically designed for situations where a secure and tight connection is required but also allows for easy disassembly. This type of fitting features a unique design with a swivel nut and two mating halves that can be easily separated. This capability is particularly useful in plumbing applications where maintenance or repairs may be necessary, enabling a plumber to disconnect and reconnect sections of pipe without cutting or damaging the fittings.

In contrast, a coupling typically provides a permanent connection between two pipe sections and does not offer a means for easy disassembly. Caps serve to seal the end of a pipe and are not intended for connections that require disassembly, while elbow fittings are designed to change the direction of pipe flow and also do not facilitate easy disassembly once installed. Thus, the union fitting stands out as the optimal choice for achieving both secure connectivity and the convenience of disassembly when needed.