Grease Interceptor vs Grease Trap: What's the Difference and Which Do You Need?

A grease interceptor and a grease trap both remove fats, oils, and grease (FOG) from kitchen wastewater before it enters the municipal sewer system. The difference is scale: a grease trap is a small, point-of-use device installed under or near a single fixture, while a grease interceptor is a large-capacity unit — typically installed in-ground or in a mechanical room — that serves the entire kitchen's drainage system. The terms are often used interchangeably, but plumbing codes, sizing requirements, and maintenance obligations differ substantially between the two.

Quick Comparison

Grease Traps: Detailed Breakdown

Grease traps — also called point-of-use (POU) traps or hydromechanical grease interceptors (HGIs) — are compact devices designed to intercept FOG from individual fixtures. They are installed in the kitchen itself, typically under a three-compartment sink, pre-rinse sink, or floor drain.

How They Work

Wastewater enters the trap and slows down inside a baffled chamber. Grease, being lighter than water, floats to the top and is retained behind the baffle. Cleaner water flows out the bottom and continues to the sewer. The separated grease accumulates in the trap until it is manually cleaned.

Pros

• Lower equipment and installation cost
• No excavation required — installs inside the kitchen
• Can be cleaned by kitchen staff in many jurisdictions (no hauler needed)
• Good solution for small operations with limited FOG output

Cons

• Limited capacity — requires frequent cleaning (often weekly)
• Only protects the fixtures it is connected to
• Can generate odors if not cleaned on schedule
• Not sufficient for high-volume kitchens under most plumbing codes

Grease Interceptors: Detailed Breakdown

Grease interceptors — sometimes called gravity grease interceptors (GGIs) — are large-volume tanks that serve the entire kitchen drainage system. They are typically buried outside the building and connected to the kitchen's main drain line before it reaches the municipal sewer connection.

How They Work

The operating principle is the same as a grease trap — gravity separation — but at a much larger scale. Wastewater enters a multi-compartment tank, flow velocity drops, and FOG rises to the surface while solids settle to the bottom. Retention time (typically 30+ minutes) allows for more thorough separation. The interceptor is pumped by a licensed grease hauler on a scheduled basis.

Pros

• High capacity handles full kitchen drainage loads
• Longer intervals between maintenance (monthly to quarterly)
• Required by code for most full-service restaurants and institutional kitchens
• Better FOG removal efficiency due to longer retention time

Cons

• Significantly higher equipment and installation cost
• Requires excavation for in-ground installation
• Professional pumping service required (cannot be cleaned by staff)
• Access point must remain accessible for pump truck — site planning required

For a deeper dive into interceptor types, specifications, and selection criteria, visit the grease interceptor resource hub.

Which Do You Need?

The answer depends on your kitchen's size, fixture count, local plumbing code, and FOG generation volume:

• Small cafe, coffee shop, or bakery with 1–3 fixtures and low FOG output: A point-of-use grease trap (15–25 GPM) may be sufficient, depending on local code.
• Quick-service restaurant or deli with fryers and multiple prep sinks: Most jurisdictions require at least a small grease interceptor (500–750 gallon).
• Full-service restaurant, hotel kitchen, or cafeteria: A grease interceptor is required in virtually all jurisdictions. Sizing depends on fixture count and flow rate — use the grease trap sizing calculator to determine the right capacity.
• Multi-tenant food court or institutional kitchen: Large interceptor (1,000+ gallons) with professional maintenance contract.

Some facilities use both: a point-of-use grease trap on high-FOG fixtures (such as a wok station or deep fryer drain) plus an in-ground interceptor on the main kitchen drain line. This two-stage approach provides redundant FOG capture and can extend interceptor pump-out intervals.

Code Requirements

Both the Uniform Plumbing Code (UPC) and International Plumbing Code (IPC) require FOG pretreatment for commercial food service establishments. The specific device type and size are determined by fixture count, flow rate, and local amendments. Key code distinctions:

• Hydromechanical grease interceptors (grease traps) must comply with PDI G-101 and/or NSF/ANSI 14.
• Gravity grease interceptors must comply with ASME A112.14.3 or local equivalent standards.
• Many municipalities specify minimum interceptor sizes (e.g., 1,000-gallon minimum) regardless of calculated requirements.

Always verify requirements with your local Authority Having Jurisdiction. FOG regulations vary significantly — check the regulations hub for state-specific guidance.

Ready to find a qualified installer or pumping service? Use the grease trap service directory to locate providers in your area.

Frequently Asked Questions

Can I use a grease trap instead of a grease interceptor?

It depends on your local plumbing code and kitchen size. Small, low-volume operations may be permitted to use a point-of-use grease trap. However, most full-service restaurants and any facility with multiple kitchen fixtures are required to install a grease interceptor. Your local plumbing authority makes the final determination.

Is a grease interceptor the same as a grease trap?

They serve the same function — separating FOG from wastewater — but differ in size, capacity, installation method, and maintenance requirements. In the plumbing industry, "grease trap" typically refers to a small hydromechanical device (under 100 lbs capacity), while "grease interceptor" refers to a large gravity separation tank (500+ gallons). Some codes and regions use the terms differently, so always clarify with your local authority.

How much does it cost to install a grease interceptor vs a grease trap?

A grease trap typically costs $200–$1,500 for the unit plus $500–$2,000 for installation. A grease interceptor runs $3,000–$15,000 for the unit plus $5,000–$25,000 for installation (including excavation and plumbing connections). Use the grease trap cost estimator to calculate ongoing maintenance expenses for either option.

How often does each need to be cleaned?

Grease traps require cleaning every 1–4 weeks, depending on FOG volume. Grease interceptors are typically pumped every 30–90 days. Both must be serviced before the grease and solids layer reaches 25% of the device's total liquid depth. Refer to the maintenance guide for detailed scheduling recommendations.

Do I need both a grease trap and a grease interceptor?

Some facilities benefit from a two-stage approach: a point-of-use grease trap on the highest-FOG fixtures combined with an in-ground interceptor on the main drain line. This is not universally required by code, but it provides additional protection and can reduce the maintenance burden on the primary interceptor. Consult with a plumbing engineer to determine the optimal configuration for your kitchen.

Author: Grease Trap Locator Editorial Team

The Grease Trap Locator editorial team covers FOG compliance, grease trap maintenance, and commercial kitchen regulations across the US and Canada. Our guides are written for restaurant owners, facility managers, and food service operators who need practical, accurate information without the fluff.