In roughing-in for a lavatory with a 1-1/2 drain, what is the maximum distance between the fixture trap and the vent?

The maximum distance between the fixture trap and the vent for a lavatory with a 1-1/2 inch drain is 3 feet. This distance is specified to ensure proper drainage and venting, which helps prevent issues like siphoning of the trap seal or inadequate airflow, leading to drainage problems or sewer gases entering the living space.

In plumbing systems, vents are essential for allowing air into the drainage system, which helps maintain proper pressure and aids in the flow of wastewater. If the vent is too far from the trap, the plumbing may not function effectively, potentially causing backups or odors due to improper drainage.

The other options represent distances that exceed this requirement, which may lead to the aforementioned issues. Maintaining this specific distance helps ensure compliance with plumbing codes and optimal performance of the drainage system.