A circuit vent is installed to serve a battery of three water closets. According to the 2022 CPC, what is the minimum size required for the circuit vent, and under what condition can it be reduced?

• 2 inches, except it can be one-half the diameter of the drain when connecting to a stack vent or vent stack.
• 2 inches, with no provision for reduction.
• 3 inches, except for residential applications where it can be 2 inches.
• 1 1/2 inches, provided it serves no more than two fixtures.