For a kitchen sink, which connection is prohibited for the trap to a vertical drain?

• A. Connecting with a double sanitary tee
• B. Using a single sanitary tee
• C. Connecting to a vented stack
• D. Connecting to a horizontal wye

Answer: (A)

When joining a sink trap to a vertical drain, the flow path and venting must be preserved with a proper fitting. A double sanitary tee is not allowed here because it creates an awkward, obstructive path with two openings that can trap debris and hinder proper venting, which can lead to slow drainage or siphoning of the trap. A single sanitary tee provides a clean, single path into the vertical stack and supports correct venting. You can also connect to a vented stack or to a horizontal wye as long as the configuration maintains slope and proper venting.