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Grease Interceptor / Trap Sizing Calculator

GPM Flow Rate and Grease Retention per IPC/UPC for Hydromechanical Grease Interceptors and Gravity Grease Interceptors

Free grease interceptor planning screen for plumbers, mechanical engineers, and foodservice consultants who want a quick source-aware check of sink compartment volume, drain time, and entered dishwasher flow before code review. Enter compartment dimensions, drain time, connected dishwasher count, and dishwasher GPM; the app returns a local GPM screen and displayed retention value.

This tool does not reproduce IPC, UPC, PDI-G101, ASME A112.14.3, or local sewer-authority sizing rules. It keeps the old sink-volume arithmetic visible, but labels the adopted-code, product-listing, dishwasher, food-waste disposer, venting, exterior gravity interceptor, inspection, and maintenance requirements as source gaps that must be verified outside the app.

Use the output as a planning note only. Final equipment selection depends on the adopted plumbing code, local FOG ordinance, AHJ interpretation, sewer authority requirements, listed product data, manufacturer installation instructions, and qualified plumbing review.

Pro Tip: Many municipalities have their own grease interceptor sizing formulas, product-listing requirements, dishwasher rules, and FOG maintenance records. Treat this screen as a starting point, then confirm the adopted code, local sewer authority ordinance, manufacturer data, and AHJ requirements before specifying equipment.

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Grease Interceptor / Trap Sizing Calculator
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How It Works

  1. Enter Sink Compartments

    Enter the length, width, and depth for each sink compartment. The app converts cubic inches to U.S. gallons and applies a local fill-factor screen.

  2. Set Drain and Equipment Inputs

    Select the local drain-time screen and enter any dishwasher count and GPM. Verify whether those fixtures are allowed to discharge through the interceptor under local requirements.

  3. Review the Local GPM Screen

    The app displays total sink volume, effective volume, sink flow, entered dishwasher flow, total local screen flow, and a rounded GPM display size.

  4. Confirm External Requirements

    Use the source warnings to verify adopted code, PDI or ASME product listing, sewer authority rules, manufacturer instructions, and qualified plumbing review before specifying equipment.

Built For

  • Plumbers doing an early sink-volume screen before checking the local code and product listing
  • Mechanical designers documenting preliminary fixture assumptions before authority review
  • Foodservice consultants comparing connected sink and dishwasher assumptions during layout planning
  • Property managers preparing questions for a licensed plumber when a foodservice tenant changes use

Features & Capabilities

Source-Aware Flow Screen

Calculates local sink volume, effective volume, sink flow, entered dishwasher flow, rounded GPM display size, and displayed retention value.

Bounded Shared State

URL sharing and autosave values are normalized before React state, calculations, reports, or PDF exports use them.

Source Boundary Warnings

Visible warnings explain that adopted code, local amendments, product listing, AHJ review, sewer authority rules, and manufacturer instructions remain outside the app.

Source Pointers

Includes pointers to ICC IPC, PDI G101, PDI certified-product listings, ASME A112.14.3/CSA B481.1, and EPA FOG pretreatment context without reproducing protected standards.

Frequently Asked Questions

No. It is a local flow planning screen only. Adopted code, local amendments, AHJ interpretation, product listing, sewer authority rules, and manufacturer instructions must be checked separately.
It depends on local code, sewer authority rules, product instructions, temperature, detergents, and discharge pattern. The app lets you enter dishwasher flow for planning, but it does not approve that connection.
No. It shows a local GPM screen for sink and dishwasher flow. Exterior gravity interceptor sizing, tank volume, retention time, traffic loading, access, materials, and maintenance requirements remain outside the app.
Treat it as a warning that the local screen exceeds the listed-size range shown in the app. Verify whether multiple listed units, an exterior interceptor, a different method, or engineered review is required.
Disclaimer: This planning screen is not a permit submittal, plumbing design, product certification, FOG ordinance compliance check, or AHJ/sewer-authority approval. Verify all requirements with the adopted code, local sewer authority, manufacturer, and qualified plumbing professional before specifying equipment.

Learn More

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