The relief vent in a multi-story building shall be what size?

The relief vent in a multi-story building is required to be the same size as the vent stack it serves. This is crucial because the purpose of the relief vent is to allow for proper air flow and pressure equalization within the plumbing system, particularly to prevent siphoning or backflow from occurring due to fluctuations in pressure. When the relief vent is the same size as the vent stack, it ensures that the venting system can effectively handle the necessary air movement that corresponds with the drainage requirements of the building.

Sizing the relief vent correctly is important to maintain the functionality of the system as a whole; if it were smaller or improperly sized, it could lead to inadequacies in venting, which might result in negative pressure in the drainage system, affecting drainage performance and possibly leading to the failure of traps. Thus, adhering to the code requirements for vent sizing helps ensure a fully functional and efficient plumbing system in multi-story constructions.