A transition coupling may be used to ___________.

A transition coupling serves a specific purpose in plumbing systems, particularly when working with different materials. This coupling is designed to connect dissimilar types of piping, such as a PVC schedule 40 tub waste and overflow to a metallic waste pipe. The importance of using a transition coupling in this case lies in its ability to create a secure and reliable joint while accommodating the different thermal expansion and contraction properties of the materials being joined.

Metal and plastic have distinct characteristics, and a standard coupling may not provide the same structural integrity or seal needed between these two types of pipes. The transition coupling typically has a rubber gasket or some means to ensure a watertight connection, which helps to prevent leaks and potential damage from water escaping from the joint.

The other options either suggest incompatible material transitions or plumbing practices that do not require a transition coupling, which makes them unsuitable for the context of this question.