Which plumbing component connects fixtures to the drainage system while allowing ventilation?

The local vent stack serves a crucial role in connecting plumbing fixtures to the drainage system while also permitting ventilation. It is designed to extend vertically from the drainage system and up through the roof, allowing air to enter the drainage piping. This ventilation is essential as it helps to prevent the formation of negative pressure within the drainage system, which could hinder the flow of wastewater and potentially lead to the siphoning of traps.

Furthermore, the local vent stack is usually positioned close to the fixtures it serves, enabling it to effectively ventilate the drainage system associated with those fixtures. By maintaining airflow, it helps to prevent undesirable sewer gases from entering the living space, thereby contributing to the overall health and safety of the environment. This makes the local vent stack a fundamental component in meeting plumbing code requirements for proper drainage and sanitation.

The other options refer to different kinds of venting or plumbing components. The main vent is designed to serve a larger area or multiple fixtures, while traps are specifically intended to prevent sewer gas entry by holding a small amount of water. Loop vents are used for different configurations and are not directly tied to the immediate connection of fixtures to the drainage system.