Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsEasy
A plumber is installing a floor sink that receives indirect discharge from a commercial ice machine. The air gap for this indirect waste connection must be at least how many inches?
- A1 inch
- B2 inches
- C1 1/2 inches
- D3 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 1 inch
For indirect waste receptors, the air gap must be at least twice the diameter of the effective opening of the drain pipe, but not less than 1 inch. Since a typical ice machine drain is often 3/4 inch or 1 inch, the minimum 1-inch rule would apply.
Why the other options are wrong
- B. This is a common minimum size for trap seals or drain pipe diameters, not necessarily the air gap.
- C. While a larger air gap is acceptable, it is not the minimum required.
- D. This is well above the minimum required air gap and typically unnecessary.
Indirect Waste Air Gap
The unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe, fixture, or appliance discharging into an indirect waste receptor.
- Prevents backflow contamination.
- Minimum 1 inch or twice the pipe diameter.
- Required for food handling, medical, and certain other equipment.
Memory trick: Air gap, no slap, keeps water clean in your lap.