What is the primary reason for installing a vent system in plumbing?

The primary reason for installing a vent system in plumbing is to allow air to enter the plumbing system to prevent vacuum formation. Vent systems are crucial for the proper functioning of drainage systems. When water drains, it creates a negative pressure or vacuum within the piping system, which can lead to slow drainage or even siphoning of water traps. By providing air access, the vent helps to equalize pressure within the system, allowing wastewater to flow freely and ensuring that traps remain filled with water to block sewer gases from entering the living space. This is essential for maintaining a healthy and functional plumbing system.