What is the purpose of a loop vent in plumbing?

A loop vent is designed specifically to improve the ventilation of a plumbing system, particularly at high points in branch intervals of the drainage system. Its primary purpose is to ensure that there is adequate airflow, which helps to equalize pressure in the drainage pipes and prevents the formation of traps that could disrupt the proper flow of wastewater.

By serving as a secondary vent, the loop vent enables the drainage system to function more efficiently and prevents issues such as siphoning or back pressure that could occur if the primary venting is compromised. This is crucial in maintaining the proper flow and drainage of wastewater from fixtures to the sewer system.

In contrast to the other options, a loop vent does not simply connect to drain lines, isolate fixtures from drains, or provide access to the main sewer line directly. Its functionality is primarily linked to enhancing the overall venting system to prevent drainage system problems.