What is the primary function of a plumbing vent?

The primary function of a plumbing vent is to equalize pressure in the drainage system. Vents allow air to enter the plumbing system, which helps maintain neutral atmospheric pressure in the pipes. This is crucial for the proper flow of wastewater and helps prevent the formation of a vacuum that could impede drainage. By allowing air to flow into the system, vents ensure that wastewater flows smoothly through the pipes and prevent siphoning of traps, which could lead to odors and sewer gases entering the living space.

While you may consider the other options, they do not capture the fundamental role of vents within the plumbing system as effectively as the correct choice. For instance, supplying hot water pertains to the water supply system rather than ventilation, and preventing air from entering is not accurate since vents are designed specifically to allow air in to avoid negative pressure. Carrying wastewater away relates more to the drainage pipes themselves rather than the function of the venting system.