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Grease Trap Sizing Calculator

Size grease interceptors for commercial kitchens based on fixture flow rates, retention time, and load factors per PDI standards.

Inputs

GPM
minutes

PDI G101: standard retention 1.5–2.5 minutes; heavy grease use (fryers) use 2–3 min; verify with AHJ

Results

Grease Trap Size

100 gallons

≈ 4 wheelbarrows

Cleaning Frequency

1 weeks

Total Flow Rate45 GPM
Grease Capacity25 gallons
How to Use This Calculator
  1. Enter the flow rate per fixture (typically 20 GPM for a 3-compartment sink).
  2. Enter the number of fixtures draining into the grease trap.
  3. Set the retention time — 30 minutes is the PDI standard minimum for interceptors.
  4. Adjust the load factor based on menu type (1.0 = light fare, 1.5 = heavy fry operation).
  5. Review Grease Trap Size in gallons — use this to specify the interceptor on your drawings.
  6. Note the Cleaning Frequency to schedule pumping service for code compliance.

What each input means

Flow per Fixture
Flow rate per fixture in gallons per minute. 3-compartment sink: 15 GPM, dishwasher: 10 GPM.
Number of Fixtures
Total number of fixtures connected to the grease trap (sinks, dishwashers, etc.).
Retention Time
Required grease retention time per PDI G101 (Plumbing and Drainage Institute) and local health codes. PDI G101 Method: size = flow × retention time; typical 1–2.5 minutes; many jurisdictions require minimum 2 minutes per fixture.
Load Factor
Multiplier for grease load intensity. 1.0 = standard, 1.5 = heavy grease (fryers), 0.5 = light use.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Flow per Fixture = 15, Number of Fixtures = 3, Retention Time = 2, Load Factor = 1 = 4 input(s) provided
  2. Calculate Grease Trap Size
    100 = 100
  3. Calculate Cleaning Frequency
    Cleaning Frequency
    1 = 1
  4. Calculate Total Flow Rate
    Total Flow Rate
    45 = 45
  5. Calculate Grease Capacity
    Grease Capacity
    25 = 25

Engine last updated . Checked against 1 independently-derived test — how we verify calculators.

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