Which joint fitting is NOT typically used with copper tubes?

The selection of a weldment as the fitting type that is not typically used with copper tubes is based on the common practices in plumbing and piping systems. Copper tubes are often joined using methods like soldering and brazing, and the fittings used in these processes include adapters, couplings, and reducers, which facilitate the connection and transition between different sizes or types of tubing.

An adapter, coupling, or reducer are designed to easily fit together with copper tubes, often requiring minimal surface preparation and allowing for efficient sealing at the joints. These fittings help in changing the direction of the flow or connecting different tube sizes without compromising the integrity of the system.

On the other hand, a weldment refers to a joint that is created by welding materials together. While some metals can be welded, copper is typically not welded in plumbing applications due to its thermal conductivity, which can lead to difficulties in achieving a strong, leak-free weld. Instead, brazing or soldering techniques are preferred for copper tubing to ensure reliable and durable connections. Hence, weldments are not practical or efficient for use with copper tubes, making this choice the correct answer.