Drainlayer Tradesman Practice Exam

In cast-iron piping, the hub is the socket at the end of a pipe or fitting that receives the end of the next section. Its purpose is to provide a joining point where two pieces can be securely connected and sealed, using a leaded joint or a compression joint, so the system stays leak-tight and properly aligned. It’s not a decorative cap, not a valve, and not a pipe support—the hub’s job is specifically to facilitate a reliable connection between pipe sections.