What do you use to join two pipes of unequal sizes?

When joining two pipes of unequal sizes, a bell reducer is the most appropriate choice. A bell reducer is specifically designed to connect pipes of different diameters in a way that allows for a smooth transition. This type of fitting typically has a larger opening at one end (the bell) and a smaller opening at the other end, making it ideal for efficiently managing changes in pipe size without creating turbulence in the flow of the fluid being transported.

By using a bell reducer, you can help ensure a proper fit and maintain the integrity of the piping system. It facilitates a gradual reduction of diameter, which is crucial in preventing pressure drops or flow restrictions that might occur with abrupt size changes.

While the other choices may serve various purposes in plumbing and piping, they are not suited for the specific task of connecting pipes of differing diameters. A bushing is used to connect smaller fittings to larger ones, but it is typically for the same kind of connection rather than to bridge two different sizes. Tapping tape is used for repairs or sealing rather than joining pipes. A union, although useful for connecting two pipes with the same diameter and allowing for easy disconnection, does not address the different sizes.