Master Plumber Practice Exam 2025 – Complete Prep Guide

The primary function of a vent system in plumbing is to prevent siphoning, which is crucial for maintaining the proper flow of waste and air in the drainage system. Vents allow air to enter the plumbing system, balancing the pressure within the pipes. This pressure equilibrium prevents the formation of a vacuum that could siphon water out of traps, which act as barriers to sewer gases. When traps dry out due to siphoning, they no longer serve their purpose, potentially allowing harmful gases to enter living spaces.

While providing drainage and enabling proper sewage flow are also important aspects of a plumbing system, these functions are primarily facilitated by the drainage pipes themselves rather than the vent system. The water supply is independent of the vent system and is managed by different plumbing components. Therefore, preventing siphoning is the most direct and critical role of a vent system in maintaining effective plumbing operations.