What is the purpose of a relief vent in plumbing?

The purpose of a relief vent in plumbing is to relieve pressure in venting systems. In a typical plumbing system, fixtures generate airflow that can create positive or negative pressure. A relief vent allows air to enter the system to equalize pressure, ensuring proper drainage and preventing potential siphoning of water from traps. This is crucial for maintaining the balance of pressure within the pipes, which helps to prevent issues such as gurgling sounds in drains or the failure of traps, leading to sewer gases entering living spaces.

The correct answer reflects an essential aspect of plumbing system performance, where adequate ventilation not only facilitates effective wastewater removal but also protects the integrity and functionality of the plumbing system as a whole. Proper venting, therefore, is critical for maintaining a healthy and effective plumbing installation.