Grease Interceptor Sizing Calculator

Size a grease interceptor for commercial kitchens based on fixture count, flow rate, and drainage period.

Inputs

Number of Sinks

Number of Dishwashers

Sink Flow Rate (GPM)

Drainage Period (min)

Tab to move between fields

Results

Required Capacity (gal)

975 gal

≈ 25 bathtubs

Standard Trap Size

500 gal

≈ 13 bathtubs

Pump-Out Frequency30 days

Total Flow Rate65 GPM

How to Use This Calculator

Enter Number of Sinks, Number of Dishwashers, and Sink Flow Rate (GPM).
Set Drainage Period (min).
Review Required Capacity (gal) and Standard Trap Size (gal).
Use Pump-Out Frequency (days) and Total Flow Rate (GPM) to inform your decision.
Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Number of Sinks

Number of Sinks	Required Capacity (gal)	Standard Trap Size
2.9	953 gal	500 gal
7.65	2,021 gal	500 gal
13	3,225 gal	500 gal
18	4,350 gal	500 gal

What each input means

Number of Sinks: Total number of kitchen sinks and prep sinks draining through the interceptor
Number of Dishwashers: Number of commercial dishwashers (typically rated at 20 GPM each)
Sink Flow Rate (GPM): Average flow rate per sink in gallons per minute
Drainage Period (min): Minutes to drain one full sink (minimum 30 min per code)

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Number of Sinks = 3, Number of Dishwashers = 1, Sink Flow Rate (GPM) = 15, Drainage Period (min) = 30 = 4 input(s) provided
Calculate Required Capacity
Required Capacity
975 = 975
Calculate Standard Trap Size
Standard Trap Size
500 = 500
Calculate Pump-Out Frequency
Pump-Out Frequency
30 = 30

Engine last updated July 26, 2026. Checked against 2 independently-derived tests — how we verify calculators.

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