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Grease Trap Pumping Schedule Calculator

Calculate FOG accumulation rate and optimal pumping frequency using the 25% rule per EPA guidance and PDI standards

Free grease trap pumping schedule calculator for restaurant managers, foodservice operators, and plumbing maintenance professionals. Enter the grease trap or grease interceptor capacity, estimated daily flow, food type (heavy grease like fried foods, moderate like general cooking, or light like bakery/deli), and operating days per week to calculate the FOG (fats, oils, and grease) accumulation rate and the recommended pumping interval based on the industry-standard 25% rule. The 25% rule states that grease traps must be pumped before FOG accumulation exceeds 25% of the wetted depth, beyond this point, grease breaks through to the sanitary sewer and the trap loses effectiveness.

Pro Tip: Most municipalities enforce the 25% rule, but the smart play is to pump at 20% to give yourself a margin of safety. A failed grease trap inspection typically results in a fine of $500 to $5,000 and can trigger enhanced monitoring. The cost of one extra pumping per year is almost always less than one fine. Track your pumping records, many jurisdictions now require a maintenance log, and a documented schedule demonstrates due diligence if there's ever a sewer backup complaint.

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Grease Trap Pumping Schedule Calculator
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How It Works

  1. Enter Trap Specifications

    Enter the grease trap capacity in gallons (common sizes: 20-50 gallon indoor point-of-use traps, 500-2,000 gallon outdoor in-ground interceptors). Select the trap type, passive (gravity), automatic (timer-operated skimming), or gravity interceptor (large outdoor unit).

  2. Describe the Operation

    Select the food establishment type: heavy grease (fried chicken, fish & chips, Chinese/Mexican), moderate grease (casual dining, pizza, general cooking), or light grease (bakery, deli, sandwich shop, coffee shop). Enter the average daily meal count or daily water flow in gallons.

  3. Set Operating Schedule

    Enter the number of operating days per week and any seasonal variation (higher volume in summer for restaurants with outdoor seating, holiday peaks for catering operations).

  4. Review Pumping Schedule

    The calculator shows the estimated FOG accumulation rate in inches per day, the number of days to reach the 25% threshold, and the recommended pumping interval. It also estimates the annual pumping cost based on typical hauler rates in your region.

Built For

  • Restaurant owners establishing a pumping schedule to comply with municipal FOG ordinances and avoid fines
  • Foodservice chain operations managers standardizing grease trap maintenance across multiple locations
  • Plumbing contractors advising food establishment clients on optimal pumping frequency after installing new grease traps
  • Municipal pretreatment coordinators evaluating whether a food establishment's self-reported pumping frequency is adequate
  • Grease hauling companies helping clients optimize their service frequency to balance cost and compliance

Assumptions

  • FOG accumulation rates are based on EPA and PDI published data for typical food establishment categories, actual rates vary significantly with menu and cooking practices.
  • The 25% rule is used as the pumping threshold, some municipalities use stricter thresholds (20% or a fixed maximum interval such as 90 days).
  • The trap is correctly sized for the flow rate, an undersized trap will accumulate FOG faster than these estimates because of reduced retention time.

References

  • EPA, Fats, Oils, and Grease (FOG) Management Guidance for Food Service Establishments
  • PDI (Plumbing and Drainage Institute), Grease Interceptor Sizing and Installation Standards
  • ASME A112.14.3, Grease Interceptors
  • Water Environment Federation, Guide for Municipal FOG Management Programs

Frequently Asked Questions

The 25% rule is the industry-standard maintenance threshold for grease traps and interceptors. It states that the combined depth of floating grease (FOG layer on top) and settled solids (food particles on the bottom) must not exceed 25% of the total wetted depth of the trap. When FOG exceeds this level, the trap's retention time is insufficient and grease passes through to the sewer. Most municipal FOG ordinances reference this threshold, and inspectors measure it with a sampling pole during compliance checks.
It depends on the trap size, food type, and daily volume. A 50-gallon indoor trap at a high-volume fried food restaurant may need pumping every 1-2 weeks. A 1,500-gallon outdoor interceptor at the same restaurant might go 30-90 days. The only reliable way to determine the correct frequency is to measure the FOG accumulation rate during the first few months and calculate when it reaches 25%. This calculator estimates the interval based on typical accumulation rates for different food establishment types.
Grease breaks through the trap and enters the sanitary sewer. In the sewer, it cools and solidifies, forming blockages called "fatbergs" that cause sewer backups. The consequences: (1) fines from the municipality, typically $500-$5,000 per violation, (2) sewer backup into your establishment or neighboring properties, creating a health hazard and cleanup liability, (3) surcharges on your sewer bill for excessive FOG discharge, and (4) potential forced closure until the grease trap is brought into compliance. Some jurisdictions escalate to criminal penalties for repeat offenders.
Biological additives (enzyme or bacteria products) can help reduce FOG accumulation rates, but they do not eliminate the need for pumping. Many municipalities explicitly prohibit using additives as a substitute for mechanical pumping. The additives emulsify grease in the trap, which can actually push it downstream to the sewer, the exact opposite of what the trap is supposed to do. If you use additives, treat them as a supplement to extend the interval between pumpings, not a replacement. Always verify that your local ordinance permits their use.
Disclaimer: This calculator provides estimated pumping schedules based on typical FOG accumulation rates for different food establishment types. Actual accumulation depends on menu, cooking methods, dishwashing practices, and flow volume. Pumping schedules must comply with local municipal FOG ordinances, which may specify maximum intervals regardless of measured accumulation. Always verify with your local sewer authority for specific compliance requirements.

Learn More

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Grease Trap Sizing, Pumping Schedules, and FOG Compliance

How grease traps and interceptors work, the 25% rule for pumping frequency, sizing by flow rate, and what inspectors look for during FOG compliance checks.

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