If a 3 inch drain enters a house, it must be attached to what size vent stack in inches?

The correct answer, which specifies that a 3-inch drain must be attached to a 3-inch vent stack, is based on plumbing standards that ensure proper drainage and ventilation within a plumbing system. The vent stack plays a crucial role in allowing sewer gases to escape and maintaining atmosphere pressure within the drainage system.

Using a vent stack that matches the size of the drain ensures that air can effectively circulate, preventing negative pressure and allowing wastewater to flow smoothly without creating blockages. A vent stack that is too small could lead to insufficient airflow, which might cause slow drainage and potential sewer gas issues in the home. This is why the standard size for the vent stack is designed to match the drain size in this scenario.