What is the maximum allowable distance from a trap to the fixture it serves?

The maximum allowable distance from a trap to the fixture it serves is traditionally specified as 24 inches. This distance ensures that wastewater effectively flows from the fixture into the trap and prevents issues such as siphoning or poor drainage. Maintaining this distance helps to minimize the chances of odors escaping or blockages occurring, which is critical for proper plumbing function.

In plumbing codes and practice, a trap serves to prevent sewer gases from entering the living space, and its proximity to the fixture is crucial for effective performance. Excessive distances could result in the trap not being able to perform effectively, leading to potential plumbing malfunctions.

Standards may vary by jurisdiction, but the 24-inch guideline represents a widely accepted measure in the plumbing industry. This is why that answer is considered correct.