To move liquid and solid wastes to the point of disposal, DWV piping must be installed at a slope. This slope is called the:

The correct term for the slope at which DWV (Drainage, Waste, and Vent) piping must be installed is "grade." The grade of the piping is crucial for ensuring that waste flows effectively by gravity to the disposal point, such as a sewer line or septic system. A proper grade helps prevent clogs and allows for efficient drainage, thereby maintaining the health of the plumbing system.

The concept of grade relates specifically to the angle or degree of slope applied to the piping, which is typically measured in inches of fall per foot of horizontal run. The recommended slope for most residential drain lines is usually around 1/4 inch per foot.

While the terms "pitch" and "angle" can refer to slopes in other contexts, in plumbing, "grade" is the standard terminology used to refer to the specific slope for drainage purposes. "Elevation," on the other hand, refers to the height or vertical position of a component relative to a fixed point, which does not directly pertain to the function of moving waste liquids and solids through piping systems.