Why is a vent stack necessary in high-pressure areas of a drainage system?

A vent stack is essential in high-pressure areas of a drainage system primarily to relieve the high pressure created by hydraulic jumps. In plumbing systems, when wastewater flows through pipes, it can encounter changes in elevation, pipe diameter, or direction—these changes can lead to fluctuations in pressure. A hydraulic jump occurs when the flow changes from a high-velocity state to a lower-velocity state, causing a sudden increase in pressure in the system.

By incorporating vent stacks, the pressure can be equalized, allowing gases to escape and preventing the potential for backing up or damaging the drainage system. Proper venting ensures that air can enter the system, facilitating smoother flow and reducing the likelihood of blockages caused by pressure build-up. This is crucial for maintaining the functionality and longevity of the plumbing infrastructure.

The other options do not accurately describe the primary function of a vent stack in this context. By focusing on relieving pressure, the role of a vent stack becomes clear in managing the dynamics of fluid flow within high-pressure areas.