Journeyman Plumber ExamPlumbing Code and RegulationsHard
A plumber is installing a water-supplied appliance in a commercial laundry room. The appliance requires an indirect waste connection. According to plumbing codes, what is the maximum vertical distance allowed between the indirect waste pipe outlet and the flood level rim of the receptor into which it discharges?
- A6 inches (150 mm)
- B1 inch (25 mm)
- C4 inches (100 mm)
- D2 inches (50 mm)
Show answer & explanationAnswer & explanation
Correct answer: D. 2 inches (50 mm)
Plumbing codes, such as the IPC and UPC, specify that the air gap for an indirect waste receptor should not be less than 1 inch but generally not more than 2 inches, or twice the diameter of the effective opening of the drain, whichever is greater, to prevent splash-out while maintaining an effective air gap.
Why the other options are wrong
- A. 6 inches is excessively large for an air gap and would almost certainly cause splash-out issues.
- B. 1 inch is often the minimum, but not the maximum for the air gap and could lead to splash-out.
- C. 4 inches is generally too large for an air gap, increasing the risk of splash-out.
Indirect Waste Air Gap
The un-obstructed vertical distance between the lowest opening of an indirect waste pipe and the flood level rim of the receptor into which it discharges, preventing backflow.
- Crucial for preventing cross-contamination.
- Minimum 1 inch, typically not more than 2 inches.
- Must be visible and accessible.
Memory trick: Two Inches Max, No Backflow Attack!