In a kitchen sink installation, the horizontal drain piping serving the sink trap shall not connect to a vertical drain by means of which configuration?

In a kitchen sink installation, the horizontal drain piping serving the sink trap shall not connect to a vertical drain by means of which configuration?

• A. A single sanitary tee
• B. A double sanitary tee
• C. A long sweep elbow
• D. A 45-degree wye

Answer: (B)

The key idea is how the trap arm transitions into the vertical drain without creating traps, dead water pockets, or venting problems. A double sanitary tee back-to-back forms two sharp junctions that can trap water and solids and disrupt proper venting, effectively acting like an unwanted trap in the line. That setup can lead to siphoning of the sink trap and sewer gas issues, so it is not allowed. Using a single sanitary fitting in the right orientation, or a smooth transition with a long sweep elbow or a 45-degree wye, keeps the flow path gradual and venting effective, preventing a trap or blockage.

The key idea is how the trap arm transitions into the vertical drain without creating traps, dead water pockets, or venting problems. A double sanitary tee back-to-back forms two sharp junctions that can trap water and solids and disrupt proper venting, effectively acting like an unwanted trap in the line. That setup can lead to siphoning of the sink trap and sewer gas issues, so it is not allowed. Using a single sanitary fitting in the right orientation, or a smooth transition with a long sweep elbow or a 45-degree wye, keeps the flow path gradual and venting effective, preventing a trap or blockage.