What is the definition of a wet vent in plumbing?

A wet vent is defined as a vertical pipe that serves two functions: it acts as both a drain and a vent for wastewater from plumbing fixtures, specifically designed to receive waste from non-water closet sources—such as sinks, showers, and other fixtures. This setup allows the wet vent to carry wastewater while simultaneously providing air circulation to prevent negative pressure within the drainage system, which is crucial for maintaining proper flow and function.

The significance of a wet vent lies in its ability to simplify plumbing design by reducing the number of separate pipes needed for drainage and venting, thus aiding in efficient space utilization and potentially lowering installation costs. By combining venting and drainage functions, wet vents help to ensure that waste can exit the plumbing system effectively while allowing air to enter, preventing siphoning action and ensuring traps remain filled with water.

In this context, it’s important to note that the other options do not accurately define the function of a wet vent. A vent for air circulation does not capture the dual purpose of drainage and venting, while a vent serving as a water source misrepresents the nature of a vent entirely. Similarly, a vent for gas lines is unrelated to the drainage and waste management aspects that define a wet vent.