The load on DWV system piping must be computed in terms of ______ values.

The load on the Drain, Waste, and Vent (DWV) system piping is computed in terms of drainage fixture units (d.f.u.) because d.f.u. offers a standardized measure that considers not only the type of plumbing fixtures but also their flow characteristics and usage frequency. This unit of measurement helps to establish a uniform basis for evaluating the potential load on a plumbing system, allowing for the efficient design and sizing of pipes, fittings, and other components according to anticipated usage.

Drainage fixture units account for both the volume of water that a fixture might discharge and the duration and frequency of use, facilitating a more accurate representation of the plumbing load within a residence. Using d.f.u. enables engineers, plumbers, and inspectors to follow the guidelines set forth in the International Residential Code to ensure that plumbing systems are adequately designed to handle the expected waste flow.

In contrast, other options like imperial gallons would focus solely on volume without considering usage patterns, hydraulic units are often used in different contexts related to pressure or flow, and cubic feet per second is more relevant to fluid dynamics rather than plumbing systems specifically designed to handle waste flow. Therefore, using drainage fixture units is the most appropriate method for calculating loads in DWV systems.