What is the fixture unit value for a 4" vent pipe?

The fixture unit value for a 4" vent pipe is indeed 36 fixture units (FU). This value is established by plumbing codes and standards to assess the load that plumbing systems can handle. In the context of vent piping, the fixture unit value represents the capacity of the vent to allow for the correct functioning of drainage systems and to prevent negative pressure that can cause siphoning or backflow.

The value of 36 FU for a 4" vent pipe indicates that it can adequately accommodate the ventilation requirements of multiple plumbing fixtures connected to the drainage system. Since vent pipes play a crucial role in maintaining proper air pressure and ensuring the smooth flow of waste, using the correct fixture unit value is essential for effective plumbing design.

In contrast, the other options provided—24 FU, 172 FU, and 342 FU—do not align with the established standard for a 4" vent pipe. Those values may correspond to other pipe sizes or configurations but not specifically for a 4" vent, which is why they are not applicable in this scenario. Understanding the correct fixture unit value is critical for compliance with plumbing codes and for ensuring the operational efficiency of plumbing systems.