What is the purpose of a plumbing vent?

The purpose of a plumbing vent is to allow air to enter the plumbing system and prevent vacuum formation. Vent pipes are essential components of a plumbing system as they connect the drainage system to the outside atmosphere. By allowing air to enter, vents help maintain neutral air pressure within the drainage system, which is crucial for the smooth flow of wastewater. Without proper ventilation, a vacuum can form when water drains, leading to slow drainage and potential blockages. Additionally, vents help to regulate the pressure, ensuring that traps maintain their water seal by preventing siphoning. This is vital for stopping sewer gases from coming back into the living space.

The other choices do not accurately capture the primary function of plumbing vents. While proper drainage is important, it is not the direct purpose of a vent, as this function is handled primarily by the drainage pipes themselves. Improving water pressure is a separate concern that is not addressed by vents, as they focus on air flow rather than pressurization. Connecting multiple plumbing lines is also not a role of vents; this function is typically handled by fittings and joints within the plumbing layout.