For a 3" waste pipe, the fixture units assigned are?

For a 3" waste pipe, the appropriate allocation of fixture units is important for ensuring that the plumbing system can handle the anticipated flow of waste. In plumbing design, fixture units are a measure of the load that a particular fixture can impose on the drainage system.

In this case, a 3" waste pipe is typically designed to accommodate larger volumes of waste and fluid, which corresponds to a higher number of fixture units. By standard plumbing codes, a 3" waste pipe can generally support a significant number of fixture units, and 36 fixture units is a common figure for this size. This designation takes into account the need for adequate flow capacity and venting to manage the waste water effectively and to prevent clogs or undue pressure build-up in the system.

Other options do not reflect the standard allocation for a 3" waste pipe. The numbers 6, 12, and 172 fixture units would typically pertain to either smaller pipe sizes or non-standard high-load scenarios, which are generally not applicable to a conventional 3" waste line, thereby reinforcing that 36 fixture units is the correct and widely accepted assignment for this size of waste pipe.