What is the function of a stack vent?

A stack vent serves a crucial role in plumbing systems by providing an extension of a vertical drainage stack above the horizontal drains. This extension allows for proper ventilation of the drainage system, which is essential for maintaining a balance of air pressure within the system. By allowing air to enter the drainage system, the stack vent prevents the formation of vacuum conditions that can lead to slow drainage or even the siphoning of traps, which can result in sewer gases entering the building.

Furthermore, stack vents ensure that gases produced in the drainage system are safely released above the roofline, minimizing the risk of harmful odors and gases entering the living spaces of a structure. This function is pivotal for both health and safety standards in building design and plumbing.