What is the maximum allowable distance of a 1 1/2 inch fixture trap from the vent fitting?

The maximum allowable distance of a 1 1/2 inch fixture trap from the vent fitting is indeed 6 feet. This distance is specifically outlined in the International Residential Code to ensure proper drainage and ventilation for plumbing fixtures.

When a trap is located too far from a vent, there is a risk that the trap may not function correctly. A vent allows air to enter the drainage system, which helps maintain proper pressure and prevents the formation of a vacuum that could siphon water out of the trap. The 6-foot requirement ensures that the fixture remains adequately vented, preventing issues such as slow drainage and sewer gas infiltration.

Maintaining this maximum distance helps to achieve a balance between effective drainage and the necessary air flow for the system to operate correctly. Distances greater than 6 feet may lead to inadequate ventilation, which can compromise the performance of the plumbing system.