What is the maximum horizontal length allowed for indirect waste piping and local waste piping handling sanitary wastes?

• A. 30 feet
• B. 20 feet
• C. 40 feet
• D. 50 feet

Answer: (A)

A key idea in indirect and local waste piping is that the discharge path must stay within a limited horizontal distance so venting can effectively protect traps and keep flow reliable. Limiting the run helps ensure the indirect waste receptor and its venting are close enough to the fixture to prevent siphonage, reduce the chance of solids building up, and minimize odors or backflow risk.

The maximum allowed horizontal length for these waste takes is 30 feet. Shorter runs are fine, but anything longer would require additional venting or a different arrangement to maintain proper drainage. The other options would exceed or not reflect this limit, which is why 30 feet is the correct maximum.