Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsMedium
A plumber is installing a fixture trap for a floor drain located in a commercial kitchen. What is the minimum trap seal depth typically required for this type of installation?
- A4 inches
- B3 inches
- C2 inches
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 4 inches
Floor drains, especially in commercial settings, often require a deeper trap seal to prevent evaporation and provide a more robust barrier against sewer gases. A 4-inch trap seal depth is a common minimum requirement.
Why the other options are wrong
- B. 3 inches is common for residential fixtures but often insufficient for commercial floor drains.
- C. 2 inches is generally too shallow for a commercial floor drain and more common for some residential fixtures.
- D. 6 inches would provide excellent protection but is typically not the minimum required depth, often exceeding code.
Commercial Floor Drain Trap Seal
The minimum vertical distance between the weir and the dip of a trap, specifically for a commercial floor drain, to maintain a water barrier against sewer gases.
- Prevents sewer gas entry into occupied spaces.
- Deeper seals resist evaporation better.
- Commercial settings often have stricter requirements.
Memory trick: Sealing Smells, Deeper Drains Dominate.