On a 4 inch mop sink waste that is extended 38 feet from its connection on a horizontal main, what is the minimum size vent required?

For a 4-inch mop sink waste extending 38 feet from its connection on a horizontal main, the minimum vent size required is 2 inches. This is based on plumbing code regulations which state that the vent size must be proportionate to the drainage pipe size and the distance from the vent connection.

The primary purpose of installing a vent is to maintain proper pressure within the drainage system, allowing wastewater to flow efficiently without siphoning traps. A 2-inch vent is adequate in handling the air flow and pressure changes for a 4-inch drainage system, given the length of the run. According to plumbing codes, larger pipes generally require larger vents, but as the total developed length of less than 40 feet is a manageable size for a 4-inch fixture, a 2-inch vent suffices.

Using any larger size, such as 3 inches or 4 inches, would be unnecessary and may complicate installation without enhancing performance. The code is designed for efficiency and practicality in accomplishing venting needs, thus confirming that the 2-inch vent is indeed the minimum size suitable for this application.