What is the primary function of a vent stack?

The primary function of a vent stack is to prevent excessive pressures in the drainage stack. Vent stacks play a critical role in maintaining the proper functioning of a plumbing system by allowing air to enter the drainage system. This influx of air is essential for balancing atmospheric pressure within the pipes, especially during the drainage process.

When wastewater flows down through the drainage system, it can create a vacuum effect or negative pressure, which, if unchecked, may lead to slow drainage or even a complete blockage. The vent stack mitigates this issue by providing a pathway for air to enter the system, ensuring that waste can flow freely and efficiently without creating pressure differentials that might impede the flow or cause traps to be emptied, leading to potential sewer gas leaks.

Understanding this function highlights the importance of proper venting in plumbing systems and illustrates why the other options do not reflect the primary function of a vent stack. For instance, while vent stacks do connect various parts of a plumbing system, their primary purpose revolves around pressure equilibrium rather than simply facilitating connections or enhancing water flow.