Master Plumber Practice Exam 2025 – Complete Prep Guide

In plumbing design, a wet venting system allows for the drainage of multiple fixtures through a common vent. For a kitchen sink that also drains a laundry tub, building codes typically require specific sizes for the wet-vented section to ensure proper drainage and venting.

The minimum size for a wet vent that services a kitchen sink in conjunction with a laundry tub is 2 inches. This size is crucial as it accommodates the potential flow from both fixtures, preventing issues such as back-pressure and ensuring that air can flow freely through the venting system to promote proper drainage. Using the appropriate pipe size helps to prevent clogs and maintains a sufficient volume of air relative to the wastewater being discharged.

Since both a kitchen sink and a laundry tub are fixtures that can generate significant waste water flow, the 2-inch size is deemed necessary to prevent draining problems and maintain an effective venting system. Hence, this size is not only compliant with plumbing codes but also supports the functional requirements of a dual fixture drainage system.