CSLB C-36 Plumbing ContractorPlanning and EstimatingHard
A plumbing contractor is preparing a bid for a commercial kitchen renovation. The blueprints show a new 3-compartment sink that will discharge wastewater. According to the Uniform Plumbing Code (UPC), what minimum size of indirect waste pipe is required for a commercial 3-compartment sink?
- A3 inches
- B4 inches
- C2 inches
- D1 1/2 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 3 inches
The UPC specifies that commercial dishwashing machines, scullery sinks, and other similar fixtures discharging through an indirect waste receptor must have an indirect waste pipe not less than 3 inches in diameter. This ensures adequate flow and prevents stoppages for high-volume commercial use.
Why the other options are wrong
- B. While 4 inches would provide ample capacity, 3 inches is the minimum required by code, making it the most cost-effective compliant option.
- C. 2 inches would be too small for the combined flow of a commercial 3-compartment sink, risking overflow and blockages.
- D. 1 1/2 inches is typically for smaller residential fixtures or individual compartments, not a commercial 3-compartment sink's combined indirect waste.
Indirect Waste Pipe Sizing (UPC)
The Uniform Plumbing Code's requirements for the minimum diameter of pipes that discharge wastewater indirectly into a drainage system, typically for fixtures like commercial sinks or dishwashers.
- Prevents cross-contamination by maintaining an air gap.
- Sizing depends on the type and volume of fixture discharge.
- Commercial scullery sinks often require larger indirect waste pipes.
Memory trick: Commercial sink: 3 inches to drain.