What size grease trap is needed for a 3 compartment sink?

PlumbingPDI G-101 & ASME A112.14.3

Commercial Grease Trap Sizing Calculator (PDI G-101)

Size commercial indoor hydro-mechanical grease interceptors (HGI) based on 3-compartment sink dimensions and plumbing fixture flow rates.

Plumbing Field StandardsPDI G-101 & ASME A112.14.3

Engineering formulations calibrated to IPC, UPC & NEC specificationsSub-Zero Cold Climate Tolerances

Quick Summary & Key Answer

Under Plumbing and Drainage Institute (PDI G-101) standards, grease trap flow rate is sized by calculating 75% of total fixture volume and dividing by a 1-minute or 2-minute drain period. A standard commercial 3-compartment sink (24"x24"x14") requires a minimum 35 to 50 GPM grease interceptor rated for 70 to 100 pounds of grease retention.

Grease retention capacity in pounds = 2 × GPM rating.
A vented external flow control tee must be installed upstream of the interceptor.
Restaurant health codes mandate cleaning grease traps when grease reaches 25% capacity.

Interactive Calculator

Adjust inputs for real-time results

Sink Compartment Lengthinches

inches

Sink Compartment Widthinches

inches

Sink Compartment Depthinches

inches

Number of Compartments

Drain Period Requirement

Calculated OutputPDI G-101 Sized

Minimum Grease Trap Flow Rate

100 GPMGPM

Grease Retention Capacity (PDI 2x Rule): 200 lbs
Total Sink Basin Capacity: 105 Gallons
Calculated Peak Discharge Flow: 79 GPM
Flow Control Device Required: Yes (Mandatory Vented Fitting)

Note: Per PDI G-101, grease capacity in pounds equals twice the GPM rating (e.g. a 25 GPM trap holds 50 lbs of grease).

PDI G-101 Sizing Formula

Failure to install a properly sized grease trap leads to municipal sewer fats, oils, and grease (FOG) fines and grease blockages.

Frequently Asked Questions

Common questions regarding this calculation and code compliance

Most commercial 3-compartment pot sinks require a 35 GPM (70 lb) or 50 GPM (100 lb) hydro-mechanical grease interceptor.