Which component of a plumbing system is described as the vertical part that receives drainage from horizontal branches?

The waste stack is the vertical conduit in a plumbing system designed specifically to receive and convey drainage from horizontal branches. It functions by collecting wastewater from multiple fixtures and transporting it downward through the system to ultimately connect to the building drain. This component is vital for maintaining proper drainage and preventing the accumulation of sewage or waste in the building's plumbing system.

Waste stacks are typically constructed of materials that can handle the corrosive nature of wastewater. Additionally, they are often required to meet specific building codes, ensuring they maintain adequate size and slope to promote efficient drainage. By functioning as the central vertical element, the waste stack plays a crucial role in the overall efficiency and safety of a plumbing system.

In contrast, other components such as the building drain, fixture branch, and vent stack have distinct roles that do not include receiving drainage from horizontal branches directly. The building drain, for instance, is the horizontal pipe that collects waste from the waste stack and directs it to the sewer or septic system. The fixture branch serves to connect individual fixtures to the waste stack but does not serve as the vertical conduit itself. The vent stack allows for air circulation in the plumbing system, which is important for maintaining proper drainage and preventing siphoning of traps, but it does not handle wastewater directly.