A loop vent connects which of the following?

A loop vent is specifically designed to connect two or more floor outlet fixtures, allowing for the proper venting of wastewater from those fixtures while helping to maintain a neutral pressure in the drainage system. When multiple fixtures are located in close proximity, such as in a bathroom setting, a loop vent provides a way to handle venting needs without requiring extensive and complicated venting arrangements.

This type of venting system serves the dual purpose of preventing the backflow of sewer gases and ensuring that the drainage system functions efficiently. By connecting to multiple fixtures, it can help balance the pressure within the drainage system, preventing potential siphoning or blockage that could compromise functionality.

While other options describe valid plumbing concepts, such as vent stacks and main drains, they do not accurately reflect the specific role and structure of a loop vent.