Grease Trap Size Calculator
Determine the correct GPM rating for your commercial kitchen interceptor. PDI-G101 compliant sizing based on sink dimensions and drainage load.
Fixture Specifications
Recommended Size
0
GPM
Total Volume
0 gal
All fixtures combined
Peak Flow Rate
0 GPM
Multi-fixture adjusted
Note: A 75% capacity factor is applied to account for displacement (dishes, pots, utensils) and avoid overflow, as per standard PDI-G101 plumbing practice. Always select the next larger standard GPM rating if your result falls between sizes.
How is Grease Trap Size Calculated? (PDI-G101)
Grease trap sizing is based on the peak volume of water that could drain through the unit simultaneously. The recognised industry standard for Hydromechanical Grease Interceptors (HGI) is PDI-G101, which our calculator follows exactly.
Enter your sink dimensions (length × width × depth in inches), the number of compartments, and the expected drainage time. Our calculator applies the displacement factor and multi-fixture logic automatically.
The Sizing Formula
Multiple Fixtures
When multiple fixtures drain into one trap, they rarely all peak at once. The standard engineering approach: 100% of the largest fixture, 50% of the second, and 25% of all remaining fixtures are summed for the design GPM.
1-Minute vs 2-Minute Drainage
A 1-minute drainage time is the conservative standard for high-volume kitchens — it results in a larger GPM requirement. A 2-minute time is allowed for smaller fixtures by some codes and yields a smaller interceptor.
Local Compliance
This tool follows PDI-G101 logic, but local plumbing codes (IPC, UPC) and your local Authority Having Jurisdiction (AHJ) may have additional requirements. Always verify your final selection with a licensed plumber before installation.
Why Does My Kitchen Need a Grease Trap?
Fats, Oils, and Grease (FOG) solidify as they cool, causing blockages in municipal sewer lines and triggering costly sanitary sewer overflows (SSOs). Most jurisdictions legally require commercial kitchens — restaurants, cafeterias, food trucks, and bakeries — to intercept FOG before it reaches the public system. The grease trap rating (GPM) must match the peak discharge flow or the unit will overflow and become non-compliant.
Frequently Asked Questions
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