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

In buildings that require a main vent stack, the future vent connection should be the same size as the full vent stack. This is important to ensure proper ventilation and air flow throughout the building's plumbing system. Matching the size of the future vent connection to the full vent stack helps maintain sufficient airflow to prevent drainage issues and maintain proper pressure within the system.

Options A, B, and C are incorrect because they do not match the correct principle of maintaining the same size as the full vent stack for the future vent connection in buildings that require a main vent stack.