Massachusetts Plumbers Journeyman Practice Exam

Where can slip joints be used in a plumbing system?

1. Outlet of the trap only

2. In vertical pipes only

3. In horizontal pipes only

4. Inlet ("house-side") of the trap only

The correct answer is: Inlet ("house-side") of the trap only

Slip joints are commonly used on the inlet or "house-side" of the trap in a plumbing system. This is where the connection is made between the trap and the horizontal or vertical pipe leading to the drain system. Slip joints provide a convenient way to assemble and disassemble this connection for maintenance or repair purposes. While slip joints can also be utilized in other parts of a plumbing system, such as in other sections of the piping, their primary and most common usage is at the inlet of the trap.