What is the maximum vertical distance allowed between the fixture drain of a sink and a horizontal combination waste and vent pipe?

• A. 6 feet
• B. 8 feet
• C. 10 feet
• D. 12 feet

Answer: (B)

The maximum vertical distance allowed between the fixture drain of a sink and a horizontal combination waste and vent pipe is set at 8 feet. This requirement ensures proper drainage and venting of wastewater from the sink, helping to maintain the plumbing system's efficiency and prevent issues such as siphoning or inadequate drainage.

When the vertical distance exceeds this limit, the potential for drainage problems increases, as the wastewater may not flow effectively into the combination pipe, and venting may become less effective, leading to possible pressure imbalances in the plumbing system. Keeping this distance within the specified maximum helps ensure that both the flow of wastewater and the evacuation of air through the venting system work efficiently, supporting the overall integrity of the plumbing installation.

This guideline is based on established plumbing codes and practices designed to promote safety and functionality in residential plumbing systems.