What type of fitting is used to connect copper tubes to threaded pipes and valves?

The most appropriate fitting for connecting copper tubes to threaded pipes and valves is an adapter. An adapter specifically allows for connections between two different types of fittings, such as transitioning from a soldered copper connection to a threaded pipe. This function is particularly vital in plumbing where you may have a copper supply line that needs to connect to a standard threaded valve or fitting.

Adapters can be designed with various ends, allowing one end to fit the copper tube and the other to accommodate the threads of a pipe or valve. This versatility makes them essential in various plumbing applications where different materials or connection types are used.

In contrast, a reducer is primarily used to connect pipes of different diameters, a coupling is meant for joining two pieces of piping of the same diameter, and a bushing is designed to reduce the size of a fitting or pipe. While these fittings have their specific applications, they do not fulfill the role of connecting copper tubes to threaded fittings as effectively as an adapter does.