Massachusetts Plumbers Journeyman Practice Exam 2026 – All-in-One Guide to Master Your Licensing Test!

The correct minimum diameter for each vent extension through a roof, in the context of preventing frost closure, is indeed three inches. This specification is essential for ensuring that the vent has adequate airflow and is less susceptible to blockages caused by ice or snow accumulation, which are common issues in colder climates like Massachusetts.

While smaller diameters may technically function as vents, they can lead to increased risks during freezing weather conditions. A three-inch diameter provides a greater volume for air to pass through, which helps to maintain proper ventilation and prevents pressure buildup in the plumbing system. This is crucial for the safe and effective operation of the plumbing system, as it allows gases and odors to exit the home without obstruction.

In contrast, smaller diameters can drastically diminish the venting capability and increase the likelihood of causing frost closure. Hence, choosing a minimum diameter of three inches aligns with best practices for plumbing venting in environments prone to freezing temperatures.