Grease Trap vs Grease Interceptor: What's the Difference?

Quick Comparison

Before diving into the details, here is a side-by-side breakdown of grease traps versus grease interceptors.

Both devices serve the same core purpose: preventing fats, oils, and grease (FOG) from entering the municipal sewer system. The main differences come down to size, capacity, and the scale of the operation they serve.

How a Grease Trap Works

A grease trap is a smaller, point-of-use device typically installed under a kitchen sink or in a nearby utility area. Wastewater flows into the trap, where it slows down and cools. Because grease is lighter than water, it floats to the top and gets retained in the trap while cleaner water flows out through the bottom outlet.

Key Characteristics

• Compact size makes them suitable for kitchens with limited space.
• Lower upfront cost means they fit the budget of smaller operations.
• More frequent cleaning is required because of their smaller capacity.
• Easier to access since they are installed indoors, usually under the sink.

Grease traps work well when your kitchen produces a moderate amount of FOG and your peak water flow rate stays below 50 gallons per minute.

How a Grease Interceptor Works

A grease interceptor uses the same gravity-based separation principle but on a much larger scale. These units are buried underground outside the building and are connected to the kitchen's entire drainage system rather than a single fixture. Wastewater enters the interceptor, passes through multiple baffled chambers, and undergoes longer retention times that allow more thorough grease separation.

Key Characteristics

• High capacity handles large volumes of wastewater from multiple kitchen fixtures.
• Less frequent cleaning due to greater storage volume, though each cleaning costs more.
• Outdoor installation requires excavation and more complex plumbing work.
• Better separation efficiency thanks to longer retention times and multiple chambers.

Grease interceptors are the standard choice for high-volume kitchens, commercial food processing facilities, and any operation where large amounts of FOG enter the drainage system.

Sizing Guidelines

Proper sizing ensures your grease trap or interceptor handles your kitchen's actual FOG output without becoming overwhelmed or requiring excessive cleaning.

Grease Trap Sizing

Most plumbing codes size grease traps based on the flow rate of the connected fixtures. A typical formula considers:

• Number of sink compartments connected to the trap
• Drain rate per compartment (usually 15–25 GPM per compartment)
• Retention time required by local code

For a standard three-compartment sink, you generally need a trap rated for 20–50 GPM.

Grease Interceptor Sizing

Interceptor sizing factors in the total kitchen drainage load:

• Number of fixtures (sinks, dishwashers, floor drains)
• Peak flow rate across all connected fixtures
• Meal volume and type of cuisine
• Local code requirements (many jurisdictions specify minimum sizing)

A qualified plumber or the local sewer authority can help you calculate the correct size. Undersized equipment leads to frequent overflows and FOG violations, while oversized equipment costs more upfront without providing meaningful benefit.

Cost Differences

Grease Trap Costs

• Equipment: $200–$1,500 depending on capacity and material (steel vs. plastic)
• Installation: $100–$500 for under-sink models
• Cleaning: $75–$250 per service visit
• Lifespan: 5–10 years for steel; 15–25 years for plastic or fiberglass

Grease Interceptor Costs

• Equipment: $2,000–$10,000+ depending on capacity
• Installation: $3,000–$10,000+ including excavation and plumbing
• Cleaning: $250–$600+ per pump-out
• Lifespan: 20–40 years with proper maintenance

While the upfront investment for an interceptor is significantly higher, the cost per gallon of FOG captured tends to be lower over the life of the equipment.

Which One Does Your Business Need?

Choose a Grease Trap If You:

• Operate a small café, deli, coffee shop, or food truck
• Have a low to moderate daily meal volume
• Produce limited FOG from your menu items
• Need a quick, affordable installation
• Have indoor space available near your primary sink

Choose a Grease Interceptor If You:

• Run a full-service restaurant, hotel kitchen, or cafeteria
• Serve a high volume of meals daily
• Prepare foods that generate heavy FOG (fried foods, sauces, baked goods at scale)
• Have multiple kitchen fixtures that produce greasy wastewater
• Are required by local code to install a larger unit

In some cases, local regulations dictate which type you must install regardless of your kitchen size. Always check with your municipal sewer authority before purchasing.

Installation Considerations

Indoor Grease Traps

• Ensure adequate clearance under the sink or in the utility area for the trap and its plumbing connections.
• Confirm that the floor can support the weight of a full trap.
• Plan for easy access to the trap for cleaning and inspection.

Underground Grease Interceptors

• You need adequate outdoor space for excavation and the interceptor vault.
• The installation must meet setback requirements from property lines, buildings, and other utilities.
• Access risers must extend to grade level so the pump truck can reach the interceptor.
• You may need permits from the local building department and sewer authority.

Find the Right Professional for Your Setup

Whether you need a grease trap serviced under your sink or a large interceptor pumped out on a quarterly schedule, the right provider makes all the difference. Search FindGreaseTrapCleaners to find experienced grease trap and interceptor service companies near you.