Rhode Island Journeyman Plumber Practice Exam

What is the minimum size for wet vent piping?

1. 1/4" OD

2. 1/2" OD

3. 3/4" OD

4. 1" OD

The correct answer is: 1/2" OD

The minimum size for wet vent piping is 1/2" OD because this size provides adequate flow capacity and drainage functionality for the fixtures connected to it. Wet venting is a configuration that allows a horizontal waste pipe to also serve the purpose of a vent for multiple fixtures, reducing the number of individual vent pipes required in a plumbing system. Using a size larger than 1/2" would not be necessary for most applications and could lead to complications with drainage and venting efficiency. Smaller sizes like 1/4" or 3/4" may not properly facilitate the necessary airflow and drainage, which can cause issues such as siphoning or inadequate venting. The standard requirement for a 1/2" OD pipe aligns with plumbing codes meant to ensure proper performance and safety in drainage and venting systems.