Guide to Grease Trap Installation and Costs

If you run a commercial kitchen or food service business, you’ll likely need a grease trap installed. Grease traps keep fats, oils, and grease (FOG) from entering your plumbing system, where they can cause clogs and environmental damage. Below, we’ll break down everything you need to know about grease trap installation, including types, steps, and how much it might cost.

What Is a Grease Trap and Why Is It Important?

A grease trap (also called a grease interceptor) captures FOG before it enters the wastewater system. It’s basically a receptacle where water has time to cool down. This allows solids to settle on the bottom and grease to rise to the top. Meanwhile, the remaining clear water can flow down the drain.

Restaurants and commercial kitchens use these systems to avoid plumbing backups, health code violations, and environmental penalties. In many areas, city or county health departments require commercial businesses to install grease traps to remain compliant.

How Much Does It Cost to Install a Grease Trap?

Grease trap installation costs vary based on a business’s specific needs, so it’s impossible to provide an estimate without more information. Some things that might affect your specific cost to install a grease trap include:

• Trap size and type (under-sink vs. in-ground)
• Material (plastic, cast iron, stainless steel)
• Labor costs in your area
• Permit fees and plumbing inspections
• Accessibility and complexity of installation

In order for grease traps to be effective, they must be properly sized, constructed, and installed into your plumbing system. Because of these specific requirements, grease traps are traditionally more expensive than other plumbing operations.

Installation is just one cost to consider. You’ll also want to account for ongoing grease trap service costs to get a more thorough picture of your final expenses.

Grease Trap Installation Types and Cost Differences

There are two main types of commercial grease trap installation — under-sink and in-ground.

Under-Sink Grease Trap Installation

Under-sink grease trap installation is the most common type of grease trap for smaller kitchens and food trucks. This system is set up directly under your main dishwashing sink, so it requires less labor to install. Because of this, it’s also a much more affordable option.

In-Ground Grease Trap Installation

Larger commercial kitchens may require in-ground traps. These require excavation by a professional plumber to install, so they’ll be a lot more expensive than a simpler under-sink system. That said, they’re far more powerful and can handle large grease volumes. 

How Do You Install a Grease Trap?

Installing a grease trap is more involved than just connecting a box to a drain, which is why most people prefer to have a plumber install the system for them. Still, if you’re interested in doing it yourself, here’s how to install a grease trap.

Step 1: Site Assessment and Planning

First, you’ll need to determine where to place your grease trap. This will require you to:

• Identify all sinks and dishwashers that will connect to the grease trap. Some local regulations require you to attach all drains to the grease trap, so you may need a centralized location.
• Check with your local authorities for building and plumbing codes, environmental regulations, and any required permits or inspections. For example, they may require you to place a grease trap outside your restaurant.

Step 2: Choosing the Right Grease Trap

Choose between an under-sink or in-ground model based on your business size and local requirements.

Once you’ve done that, you need to narrow down your selection further based on your flow rate (measured in gallons per minute). It should match your kitchen’s discharge needs and be able to keep up with the capacity of all sinks and appliances that hook up to the system.

Also, select the proper material. Stainless steel is durable and corrosion-resistant, while plastic options may be more affordable.

Step 3: Preparing the Installation Area

After you’ve chosen the site and the trap itself, it’s time to begin the grease trap installation.

• Shut off water supply lines and remove any fixtures or cabinets obstructing access.
• For under-sink models, install wall or floor brackets to secure the unit.
• For in-ground models, demolish the floor area, excavate the designated area, and prepare a stable concrete base.

Step 4: Plumbing the Grease Trap into the System

No matter which system you’ve chosen, integrating it into your plumbing system works basically the same.

• Connect the inlet pipe from your sink or fixture to the grease trap’s inlet port.
• Connect the outlet pipe to your existing wastewater system, ensuring a gentle downward slope for proper flow.
• Use proper seals and fittings to prevent leaks or backflow.

Step 5: Testing and Code Compliance Check

Make sure everything is working correctly with these testing steps:

• Turn on the water to ensure the system flows as expected.
• Watch for any signs of leaks, poor flow, or improper grease separation.
• Adjust any connections or seals if you notice any issues.
• Schedule a formal inspection if required by your city or county.

Step 6: Final Setup and Staff Training

Once your grease trap is installed, you have to make sure your staff knows how to use it.

• Train kitchen staff on what can and cannot go down the drain to protect the grease trap.
• Explain how to monitor the grease level and when to schedule pumping/cleaning.
• Post maintenance logs and contact info for emergency service near the trap area.
• Set reminders for regular service and inspection based on usage and local regulations.

Is Professional Installation Required?

While it's possible to install a small under-sink unit with basic plumbing knowledge, most local codes require licensed professionals for proper installation, especially for in-ground traps. Incorrect installation can lead to leaks, backups, or failed inspections. Hiring a professional provides peace of mind and avoids the possibility of downtime at your business.

Why Regular Grease Trap Maintenance Matters

After installing a grease trap, you’ll need to keep it clean. Neglecting maintenance and a regular pumping schedule can result in foul odors, plumbing backups, and even shutdowns due to health code violations. This is especially true of grease traps in restaurants that are subjected to tons of FOG every day.

When you clean your grease trap regularly, you’ll also increase the lifespan of your system.

How Often Should a Grease Trap Be Cleaned?

On average, you should clean your grease trap every one to three months. Of course, this varies depending on how quickly it fills up. A general rule of thumb is to have your grease trap cleaned when it reaches about a quarter of its capacity. That said, local regulations may set minimum cleaning intervals for you to follow.

Signs you’re overdue for a cleaning might include:

• Slow drainage
• Grease odors
• Visible buildup

Can You Clean a Grease Trap Yourself?

You can typically clean a small under-sink trap yourself. But large or in-ground systems? Those require professional pumping and cleaning equipment. The grease must also be taken to an approved disposal or recycling center. Mistakes in the cleaning process can result in code violations or plumbing damage.

Keep Grease in Check, Not in Your Pipes

Thinking about installing a grease trap? Don’t cut corners. While grease trap installation costs can vary, a well-installed and regularly serviced trap saves thousands in repairs and fines. 

When you’re ready to move forward, contact Roto-Rooter for a professional quote and guidance. We’ll provide a free, no-pressure estimate. And if you choose us, our expert grease trap installation will help you meet every local regulation.