Which type of vent connects at the junction of two fixture drains and serves as a vent for both fixtures in a vertical position?

The common vent is a type of vent designed specifically for connecting at the junction of two fixture drains. This configuration allows it to function as a shared vent for both fixtures when installed in a vertical position. The common vent effectively connects two plumbing fixtures, helping to equalize pressure within the drainage system and preventing the siphoning of trap seals in either fixture.

This type of vent is particularly useful because it minimizes the amount of vent piping required, enhancing the efficiency of the plumbing system. It serves to provide adequate ventilation for both fixtures, ensuring they can drain properly without creating a vacuum that would hinder their function.

In contrast, an individual vent serves only one fixture, a stack vent extends vertically from the drainage system above the highest fixture, and a branch vent provides ventilation to a group of fixtures draining into the same stack but does not connect at the junction of two fixture drains. Each of these other vent types has its own specific application in plumbing design and codes, but the common vent is distinct in its capacity to serve two fixtures simultaneously.