If more than 10 feet of vertical piping is used, what is the requirement for the vent pipe?

The requirement for the vent pipe, when more than 10 feet of vertical piping is used, is that it must continue full-size through the roof. This is important because a vent pipe is designed to allow air to enter the plumbing system, which helps prevent vacuum conditions that can disrupt drainage and cause positives pressure issues. Maintaining the full size of the vent pipe ensures that it functions effectively, providing adequate airflow and pressure relief.

When the vent pipe is reduced in size or otherwise restricted, it may not allow sufficient airflow, which can lead to slow drainage or even siphoning of traps in the plumbing system. If the pipe were capped off, it would completely impede air flow, leading to far more severe issues. Similarly, not maintaining the vent pipe at full size can compromise the entire plumbing system's ability to operate properly. Therefore, keeping the vent pipe at full diameter is critical for the overall functionality and safety of the plumbing system.