Master Plumber Practice Exam

A vent line serves the primary purpose of preventing sewer gas from entering the building. It achieves this by allowing air to enter the plumbing system, which aids in maintaining proper atmospheric pressure within the pipes. When wastewater drains, it creates a vacuum that could pull sewer gases into the building if there were no venting system in place. By equalizing the pressure and providing a pathway for gases to escape safely to the outdoors, vent lines ensure a healthy and safe environment.

The other options, while related to plumbing, do not accurately capture the primary function of a vent line. Drainage is facilitated by the system’s design and gravity, not by venting itself. Water supply is managed through supply lines, which are unrelated to the venting process. Lastly, connection to the main sewer involves waste disposal rather than the management of venting and gases, further supporting the distinct role of vent lines in plumbing systems.