Commercial Grease Trap Requirements: Does Your Restaurant Need One?

If you're opening a restaurant, taking over an existing food service location, or renovating a commercial kitchen, one of the first regulatory questions you'll face is whether you need a grease trap — and if so, what kind, what size, and how to get the required permits.

The answer for most restaurants is straightforward: yes, you almost certainly need a grease trap. But the specific requirements — the type of trap, the sizing calculations, the permit process, and the ongoing maintenance obligations — vary significantly depending on where you're located.

This guide covers who needs a grease trap, what the requirements look like across different jurisdictions, how sizing is determined, exemptions that may apply, and how to navigate the permit and installation process.

Who Is Required to Have a Grease Trap?

In the United States, grease trap requirements are set at the local level — typically by your city or county's water and sewer authority, in conjunction with plumbing codes adopted from either the Uniform Plumbing Code (UPC) or the International Plumbing Code (IPC).

While specific language varies, the general rule is the same virtually everywhere: any food service establishment (FSE) that discharges wastewater containing fats, oils, and grease (FOG) into a public sewer system must have a grease trap or grease interceptor.

This typically includes:

• Full-service restaurants — dine-in with full kitchens
• Fast food and quick-service restaurants
• Cafeterias and buffets — including those in schools, hospitals, and corporate campuses
• Bakeries and dessert shops — any establishment that uses fats or oils in food preparation
• Bars and pubs — if they prepare food on-site
• Catering companies — with fixed kitchen facilities
• Grocery stores and supermarkets — if they have delis, hot food bars, or in-store kitchens
• Food trucks and mobile vendors — if they connect to a sewer system at their base of operations
• Hotels and resorts — with on-site restaurants or banquet kitchens
• Institutional kitchens — prisons, military facilities, nursing homes

The common thread is food preparation involving fats, oils, or grease that could enter the sewer system through dishwashing, pot washing, or floor drains.

Types of Grease Traps: What's Required?

Jurisdictions generally recognize two types of grease control devices, and the one you need depends on your operation's size and flow rate.

Grease Traps (Passive, Indoor)

These are smaller units, typically ranging from 20 to 100 gallons, installed inside the building — usually under a sink or in the floor near kitchen fixtures. They work by slowing down the flow of wastewater, allowing grease to float to the top and solids to settle to the bottom while relatively clean water passes through.

Best for: Small restaurants, cafes, food trucks, and low-to-moderate volume kitchens.

Pros: Lower installation cost ($200-$1,500), easier to clean, no excavation required.

Cons: Limited capacity, requires more frequent cleaning (weekly to monthly for some), not suitable for high-volume operations.

Grease Interceptors (Large, In-Ground)

These are large buried tanks, typically ranging from 500 to 3,000+ gallons, installed outside the building in the ground. They handle much higher flow rates and provide greater separation capacity.

Best for: Full-service restaurants, high-volume kitchens, hotels, institutional food service.

Pros: Higher capacity, less frequent pumping needed (monthly to quarterly), handles high flow rates.

Cons: Higher installation cost ($3,000-$15,000+), requires excavation, requires professional pumping with a vacuum truck.

Many jurisdictions specify a threshold — often based on flow rate — above which an in-ground interceptor is required instead of an indoor trap. For example, some cities require an interceptor for any fixture with a flow rate above 50 gallons per minute.

How Grease Trap Sizing Is Determined

Getting the right size is critical. An undersized grease trap won't meet code requirements and will overflow. An oversized one costs more to install and maintain than necessary.

Most jurisdictions use one of two sizing methods:

Method 1: Flow Rate Calculation (Most Common)

This method, used in most UPC and IPC jurisdictions, calculates the required trap size based on the flow rates of the kitchen fixtures connected to it. The basic formula is:

Trap size (GPM rating) = Total fixture flow rate (GPM) x Drainage load factor

Each fixture type has a standardized flow rate. For example:

Your licensed plumber adds up the flow rates of all connected fixtures and applies any local adjustment factors to determine the minimum required trap or interceptor size.

Method 2: Seating Capacity / Meals Served

Some jurisdictions use a simpler method based on restaurant seating capacity or estimated daily meals served. This is less precise but faster. A typical formula might require 1 gallon of interceptor capacity per meal served per day, with minimum sizes based on seat count.

What Gets Connected?

Generally, the following fixtures must be connected to the grease trap:

• Three-compartment sinks (pot sinks)
• Pre-rinse sinks and spray stations
• Commercial dishwashers
• Floor drains in the kitchen area
• Wok stations and cooking equipment drains
• Mop sinks (in some jurisdictions)

The following are typically not connected to the grease trap:

• Restroom fixtures (toilets, bathroom sinks)
• Hand sinks in dining areas (some jurisdictions)
• Dishwashers that discharge to a separate waste line (check local codes)

Permit Requirements: What to Expect

Installing a grease trap or interceptor is not a do-it-yourself project. It involves permits, licensed contractors, and inspections. Here's the typical process:

1. Contact Your Local Authority

Before doing anything else, contact your city or county's water and sewer authority (sometimes called the wastewater division, FOG program, or pretreatment department). They will tell you:

• Whether a grease trap or interceptor is required for your type of establishment
• What sizing method they use
• What permits are needed
• Any specific installation requirements (location, materials, access clearances)

2. Hire a Licensed Plumber

A licensed commercial plumber will assess your kitchen layout, calculate the required trap size, and prepare installation plans. For in-ground interceptors, you may also need an excavation contractor.

3. Submit Permit Applications

You'll typically need:

• Plumbing permit from the building department — covers the installation and plumbing connections
• FOG discharge permit from the water/sewer authority — authorizes your grease discharge and establishes maintenance requirements
• Health department approval (in some jurisdictions) — confirms the installation meets food safety standards

The permit application usually requires a site plan showing the trap location, plumbing diagrams, and the trap specifications (manufacturer, model, capacity, flow rate).

4. Installation and Inspection

After your permits are approved, the plumber installs the trap. An inspector from the building department and/or water authority will then inspect the installation to verify it meets code requirements before you're cleared to operate.

5. Ongoing Compliance

Once installed, your permit will include ongoing maintenance requirements, typically:

• Regular pumping on a specified schedule (usually at least quarterly)
• Maintaining cleaning records and disposal manifests
• Periodic inspections by the water authority
• Annual permit renewal (in some jurisdictions)

Exemptions: Who Might Not Need a Grease Trap?

While most food service establishments need a grease trap, some jurisdictions offer limited exemptions. These vary widely, but common exemptions include:

• Establishments with no food preparation on-site — For example, a convenience store that only sells pre-packaged food and beverages with no cooking or dishwashing.
• Coffee shops with no food prep — Some jurisdictions exempt businesses that only brew coffee and serve pre-packaged pastries, with no cooking, frying, or dishwashing involving grease.
• Establishments on septic systems — If your building is not connected to a municipal sewer system, the municipal FOG ordinance may not apply. However, your septic system permit may have its own grease management requirements.
• Very low-volume operations — Some cities offer waivers for establishments that can demonstrate extremely low grease output, though these are rare and usually require periodic review.

Important: Do not assume you qualify for an exemption. Contact your local authority to confirm. Operating without a required grease trap because you assumed you were exempt is not a valid defense against a violation.

What Happens If You Don't Comply?

The consequences of not having a required grease trap — or not maintaining one properly — are serious and escalating:

• Violation notices and fines: First-time violations often start at $250-$1,000, but fines can reach $2,000-$10,000 per day for ongoing non-compliance.
• Mandatory installation orders: If you don't have a trap and are required to, you'll receive an order to install one within a specified deadline (often 30-90 days).
• Increased monitoring: Non-compliant businesses are placed on more frequent inspection schedules.
• Sewer surcharges: Some municipalities charge additional fees to non-compliant businesses to offset the cost of dealing with grease in the sewer system.
• License suspension: In severe cases, your food service license or business license can be suspended until compliance is achieved.
• Liability for sewer damage: If grease from your establishment causes a sewer blockage, overflow, or environmental contamination, you can be held financially responsible for cleanup, repairs, and any resulting damages to neighboring properties.

The EPA estimates that FOG causes approximately 47% of all sanitary sewer overflows in the United States. Municipalities take this seriously, and enforcement has been increasing steadily.

Requirements by Jurisdiction: Key Differences

While the basics are consistent (you need a trap, it must be properly sized, and you must maintain it), specific requirements vary. Here are some notable differences across major jurisdictions:

See our state-by-state compliance guide for more specific information about requirements in your area.

How to Get Started

If you're opening a new restaurant or need to bring an existing one into compliance, here's your action plan:

1. Contact your local water/sewer authority to confirm requirements for your establishment type.
2. Hire a licensed commercial plumber experienced with grease trap installations in your jurisdiction.
3. Get the right permits before any work begins.
4. Install the correct type and size of grease trap or interceptor.
5. Pass the required inspections.
6. Set up a maintenance schedule with a licensed grease trap pumping company.
7. Keep meticulous records of all cleanings, pumpings, and inspections.

The upfront cost and effort are real, but they pale in comparison to the fines, legal liability, and potential business disruption of non-compliance.

Need help finding a grease trap service provider or getting quotes for installation and maintenance? Request a free quote from companies in your area.

Related articles:

• Grease Trap Installation: Cost, Process, and What Restaurant Owners Need to Know
• Grease Trap Size Guide: What Size Does Your Restaurant Need?
• FOG Compliance for Restaurants: A Complete Guide to Fats, Oils & Grease Regulations
• Opening a Restaurant? Everything You Need to Know About Grease Traps