What escapes the sanitary drainage system through the vent stack?

The function of the vent stack in a sanitary drainage system is primarily focused on providing air circulation to the system. This air circulation helps to maintain proper pressure within the drainage pipes and allows for the efficient removal of waste. The vent stack also serves to release gasses and odors that can accumulate in the drainage system.

When fixtures drain into the sanitary system, air is displaced. The vent stack compensates for this displacement by allowing gasses—such as sewer gas, which can contain methane and other potentially harmful compounds—to escape safely into the atmosphere. If the venting is inadequate, these gasses can build up in the plumbing, leading to poor drainage performance and even dangerous conditions within the home.

In contrast, liquid waste, solid waste, and pesticides predominantly flow through the pipes designed for drainage and are contained within the sanitary drainage system unless there's a failure or backup. Therefore, the primary role of the vent stack is to facilitate the escape of gasses and odors, ensuring a functional and safe sanitary drainage system.