Grease Trap Sizing Guide for Florida Restaurants

The right grease trap or interceptor size depends on three factors: your fixture flow rate, your menu type, and your local Florida building code requirements. An undersized unit will overflow, fail inspections, and potentially cause sewer backups. An oversized unit wastes money on installation and may still require the same pump-out frequency. Getting it right the first time saves thousands of dollars over the life of your equipment.

For most Florida restaurants, you'll need either an interior grease trap rated at 20-100 GPM or an underground grease interceptor with 500 to 2,000 gallons capacity.

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Understanding PDI Sizing Standards

The Plumbing & Drainage Institute (PDI) sets the industry standards for grease trap sizing. Two standards apply:

PDI-G101 — Gravity Grease Interceptors (passive traps)

• Rates traps by flow rate in gallons per minute (GPM)
• Standard sizes: 10, 15, 20, 25, 35, 50, 75, and 100 GPM
• Used for indoor, point-of-use installations

PDI-G102 — Automatic Grease Removal Devices (AGRD)

• Self-cleaning units that automatically skim grease
• Higher cost but lower manual maintenance
• Must still meet flow rate requirements

For underground interceptors, the relevant standard is ASME A112.14.3, which sizes units by liquid capacity in gallons.

How to Calculate Your Required Flow Rate

The basic formula for sizing a grease trap uses the fixtures connected to it:

Step 1: List All Connected Fixtures

Identify every plumbing fixture that drains through the grease trap:

• 3-compartment sinks
• Pre-rinse sinks
• Dishwashers (commercial)
• Mop sinks
• Floor drains in cooking areas
• Wok stations
• Prep sinks

Step 2: Determine Fixture Flow Rates

Each fixture type has a standard drainage fixture unit (DFU) rating:

Step 3: Calculate Total Flow Rate

Add the GPM values for all fixtures that will drain simultaneously during peak operations. This is your minimum trap size.

Example calculation:

• 1 three-compartment sink: 20 GPM
• 1 pre-rinse sink: 15 GPM
• 1 commercial dishwasher: 20 GPM
• 2 floor drains (2"): 10 GPM each = 20 GPM
• Total: 75 GPM

This kitchen needs at minimum a 75 GPM grease trap or an underground interceptor.

Step 4: Apply Menu Adjustment Factor

Heavy FOG menus require upsizing:

• Light FOG (sandwich shop, bakery, coffee shop): Use calculated size
• Medium FOG (casual dining, pizza, Mexican food): Multiply by 1.25
• Heavy FOG (fried chicken, Chinese, fish fry, deep-fry heavy): Multiply by 1.5

Using our example with a heavy-fry menu: 75 GPM x 1.5 = 112.5 GPM — you need an underground interceptor.

Interior Grease Trap Sizes (20-100 GPM)

Interior grease traps are point-of-use devices installed under sinks or on the floor. Standard sizes available:

Interior trap limitations:

• Maximum practical size is 100 GPM — above this, an underground interceptor is required
• Must be cleaned frequently (weekly to biweekly)
• Some Florida counties do not accept interior traps for full-service restaurants regardless of size

Underground Interceptor Sizes (500-2,000+ Gallons)

Underground grease interceptors are required for most full-service Florida restaurants. Standard sizes:

Key considerations:

• Larger interceptors cost more to install but may reduce pump-out frequency
• The "25% rule" means a 1,000-gallon interceptor needs service when FOG reaches 250 gallons
• Service costs scale with size — a 2,000-gallon pump-out costs more than a 500-gallon one

When You Need to Upgrade

Signs that your current grease trap or interceptor is undersized:

• Frequent pump-outs needed (more often than your county's minimum requirement)
• Repeated FOG inspection failures for exceeding 25% capacity
• Slow drains even shortly after pump-out service
• Menu changes — adding a fryer or expanding kitchen capacity increases FOG load
• Increased business volume — more covers means more FOG
• Grease visible in drain lines downstream of the trap

If you experience any of these, consult a licensed plumber or engineer to evaluate whether you need a larger unit. Contact a grease trap service company in your area — many offer sizing consultations.

Florida Building Code Requirements

The Florida Building Code (FBC) aligns with the International Plumbing Code (IPC) with Florida-specific amendments. Key sizing requirements:

1. All commercial food service establishments must have grease removal equipment
2. Sizing must follow PDI-G101 (interior traps) or ASME A112.14.3 (underground interceptors)
3. Local authority (county/city building department) has final approval on sizing
4. Permits required for installation of any grease removal equipment
5. Professional installation — must be installed by a licensed plumber
6. Inspection required before system goes into service

Additionally, your county's FOG program may have requirements that exceed the state building code. Check with your county's environmental services department.

Common Sizing Mistakes

Mistake 1: Sizing only for current fixtures Plan for your full kitchen buildout, not just what's installed today. Adding a dishwasher or fryer later means your trap is suddenly undersized.

Mistake 2: Ignoring the menu factor A 50 GPM trap might handle the flow from a salad-focused restaurant, but the same fixtures in a fried chicken restaurant need 75 GPM due to higher FOG output.

Mistake 3: Choosing the cheapest option A $300 undersized trap that overflows monthly costs far more than a $1,500 properly sized unit that runs cleanly between quarterly service appointments.

Mistake 4: Not consulting local code Florida has 67 counties with varying FOG requirements. What works in one county may not meet code in another. Always confirm with your local building department before purchasing.

Mistake 5: DIY sizing without professional input While this guide provides general guidance, your final sizing should be confirmed by a licensed plumber or engineer who can evaluate your specific fixtures, layout, and local requirements.

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