What is the fixture unit value for a 5" vent pipe?

The fixture unit value of a plumbing installation is essential for determining the load that a plumbing system can handle without overflowing, backing up, or otherwise failing. In the context of vent pipes, the size and configuration directly affect their capacity.

A 5" vent pipe is capable of accommodating a significant number of fixtures, and its larger diameter allows for greater air flow and airflow stabilizing capabilities, which is critical for venting. This is why a 5" vent pipe is associated with a higher fixture unit value, such as 420 fixture units.

The value of 420 fixture units reflects the ability of a 5" pipe to serve a large number of plumbing fixtures effectively. This enables it to handle increased drainage flow and maintain the necessary air pressure within the drainage system, which is crucial to prevent siphoning and ensure that all connected fixtures operate properly.

The other choices pertain to either smaller pipe sizes or are not representative of the capacity of a 5-inch vent pipe. A lower fixture unit value would not reflect the size and capability of a 5" pipe, confirming that 420 fixture units is the accurate and logical choice for this question.