In a DWV system, what is primarily transported by the Waste Stack?

In a Drainage, Waste, and Vent (DWV) system, the Waste Stack is designed specifically to transport wastewater away from fixtures towards the sewage system or a septic tank. Wastewater consists of water mixed with contaminants, such as human waste, food particles, and other organic matter that needs to be removed from a building to maintain sanitary conditions.

The primary function of the Waste Stack, therefore, is to handle this flow of wastewater. Wastewater is essential in the context of a DWV system, as it's crucial for the effective removal of waste materials, thus preventing blockages and ensuring a hygienic environment.

While air, water, and rainwater have roles in the overall plumbing system, they do not represent the primary function of the Waste Stack. Air is typically managed through venting, water can be part of different systems (like supply lines), and rainwater is usually directed through a separate drainage system (like stormwater management) rather than being handled by the Waste Stack. Hence, recognizing that the Waste Stack’s main responsibility is the transport of wastewater is vital for understanding its role in the plumbing system.