Which type of venting method connects back to a stack vent?

The correct answer focuses on the loop venting method, which is specifically designed to connect back to a stack vent. Loop vents are employed to provide ventilation to a plumbing fixture while maintaining a connection to the main stack vent. This configuration allows air to flow toward the stack, which helps prevent siphoning and maintains proper pressure balance in the drainage system.

A loop vent works effectively by being installed in a manner that allows it to rise above the flood level of the fixture it serves and then return to the stack. This not only enhances the performance of the venting system but also supports the prevention of trap loss, ensuring that traps do not become empty and subsequently allow sewer gases to enter living spaces.

While other types of vents, such as stack vents, branch vents, and common vents, serve crucial roles in a plumbing system, they do not specifically return or connect back to a stack in the same way a loop vent does. Stack vents primarily serve to vent the drainage system directly, branch vents provide ventilation to individual fixtures, and common vents serve to connect two fixtures on a common horizontal drainage line. Thus, loop vents are uniquely positioned to tie back to stack vents while fulfilling their designated purpose of enhancing venting efficiency.