What type of fitting would typically be used to connect two segments of pipe of different diameters?

A reducer is the correct type of fitting used to connect two segments of pipe with different diameters. This fitting allows for a smooth transition from a larger diameter pipe to a smaller diameter pipe or vice versa. The design of a reducer helps maintain the flow of fluids by gradually tapering the diameter, which minimizes turbulence and pressure loss during the transition.

In plumbing and piping systems, using a reducer is essential when the diameter of the pipes being connected differs. For example, if a larger pipe conveys water and needs to connect to a smaller pipe for drainage or distribution, a reducer ensures a proper fit and optimal flow characteristics.

While couplings are designed to connect pipe segments of the same size, 90° elbows allow for a change in direction but do not accommodate difference in diameter. Caps are used to seal the end of a pipe and do not facilitate connections between different pipe sizes.