What is the diameter of the vent pipe required for a 3-inch drain?

The diameter of the vent pipe required for a 3-inch drain is determined by plumbing codes and standards that ensure proper venting and drainage. A typical guideline in plumbing is that the diameter of the vent pipe should be at least half the diameter of the drain pipe. For a 3-inch drain, a 2-inch vent pipe is standard because it effectively allows air to flow, which helps to equalize pressure and prevent siphoning of trap seals while still meeting the necessary requirements for proper venting.

Using a vent pipe that is too small can lead to inadequate air flow, which in turn can cause drainage problems; on the other hand, a vent pipe that is too large does not significantly enhance the system's performance and can be unnecessarily costly. Therefore, a 2-inch vent pipe for a 3-inch drain is not only compliant with regulations but also effective in maintaining a balanced drainage system.