Define "vent stack".

A vent stack is defined as a vertical pipe that allows air to enter the drainage system. This function is crucial for maintaining proper air pressure within the plumbing system, which in turn facilitates the smooth flow of wastewater and prevents the formation of vacuum conditions that could disrupt drainage. Vent stacks provide a means to ventilate sewage gases safely to the outside atmosphere, making them essential for health and safety in plumbing applications.

The correct understanding of a vent stack emphasizes its role in allowing air to enter the drainage system, which is necessary for the proper function of traps and fixtures. Without adequate venting, plumbing systems can experience issues such as slow drainage or the siphoning of trap seals, leading to odors and potential health hazards. Thus, the vertical orientation and air movement associated with a vent stack are fundamental to its purpose in the plumbing code.