The total area of vents through the roof must equal that of the house drain, with a minimum requirement of what?

The minimum requirement for the total area of vents through the roof being equal to that of the house drain is a 3-inch stack. This choice aligns with plumbing codes that dictate venting practices. A 3-inch vent stack is commonly recognized as the minimum size that can adequately provide the necessary ventilation for a drainage system to function properly, ensuring that air can enter the plumbing system and prevent the formation of vacuum conditions that could impede drainage.

In a plumbing system, the purpose of venting is to allow sewer gases to escape and to equalize pressure in the waste pipes, supporting the effective flow of wastewater. The 3-inch dimension is well within the necessary parameters to meet these requirements for typical residential systems. A larger vent, such as a 4-inch or 6-inch stack, while providing increased capacity, is not mandated as a minimum and would exceed the necessary requirements for effective venting in most scenarios.

The choice of a 2-inch stack does not provide enough area to manage the airflow needed for a standard house drain, thus it does not meet the minimum requirement outlined in plumbing codes. Therefore, the 3-inch stack represents the correct answer based on established plumbing standards.