What is the purpose of a vent in a plumbing system?

The primary purpose of a vent in a plumbing system is to provide pressure balance within the drainage system. Vents help to equalize air pressure in the pipes, allowing wastewater to flow freely without creating a vacuum. This pressure balance is crucial because, without proper venting, a vacuum could form when water flows through the pipes, potentially leading to slow drainage or even the siphoning of water from traps, which creates pathways for sewer gases to enter the living spaces.

The act of venting enables the quick and efficient movement of waste and prevents obstructions caused by air pressure differences. It also allows for the escape of sewer gases, maintaining air quality within the home. The proper venting system prevents back pressure and ensures that waste can effectively travel from fixtures to the sewer or septic system without hindrance.

Other choices mention functions like draining liquid waste, directing rainwater, or supporting fixture installation, but these functions are not the primary role of a vent in a plumbing system.