How Does a Grease Trap Work?

Ever wondered how restaurants keep their plumbing clean despite the relentless flow of greasy dishwater? The answer is a clever device called the grease trap.

These hidden heroes of commercial kitchens—and even some homes or multifamily buildings—are essential for preventing fats, oils, and grease (commonly known as FOG) from clogging up pipes and wreaking havoc on plumbing systems.

Grease traps separate these pesky substances from wastewater, ensuring smooth and trouble-free drainage. They also keep your plumbing in top shape, protect our environment by preventing harmful pollutants from entering our waterways, and are mandatory for any facility that disposes of FOGs in New York City.

How does a grease trap work? This article breaks down their function and lets you know how they protect our kitchens and sewer systems.

Grease Trap Basics

Grease traps seem simple, but they have numerous components that stop fats, oils, and grease from clogging your drains.

Components of a Grease Trap

• Inlet: This is where the wastewater, loaded with FOG, enters the trap. It’s positioned to ensure a smooth flow and begins the separation process.
• Baffles: The baffles control the inside of the trap. They slow down the incoming water, allowing gravity to take over. From there, denser food particles and grease settle or float.
• Separation Chamber: This chamber is the most important part of the grease trap. It slows wastewater down further, giving FOG and the water time to separate. Grease and oils float to the top, while solid food particles sink to the bottom.
• Outlet: Once the water and FOG separate, the water exits the trap through the outlet. It’s below the grease layer, so only clean water flows out. The grease and oil stay in the trap.

These components combine to create a simple tool that keeps your pipes grease-free and functional.

How Does a Grease Trap Work?

Grease traps sound hi-tech, but they’re pretty simple. Here’s how they work:

Step 1: Wastewater Enters the Trap

Wastewater with fats, oils, and grease flows into the grease trap through the inlet. The trap design slows down the water’s momentum so the rest of the system can do its job.

Step 2: Separation of FOG from Water

The water’s velocity decreases within the trap, allowing the natural forces of gravity and density to take over. FOG is lighter and less dense than water, so it rises and floats on the surface. Heavier food particles sink to the bottom because they’re denser.

Step 3: Accumulation of FOG in the Trap

Next, FOG accumulates at the top of the trap. It forms a distinct layer of grease and oil held back by strategically placed baffles. These baffles stop the grease from entering the wastewater flow heading to the sewer system.

Step 4: Clean Water Exits the Trap

The water is now mostly free of FOG and solid waste. It flows through the outlet at the bottom of the grease layer. This stage makes it so that only clean water makes it to the sewage system, reducing the risk of blockages and contamination.

This process works because of the differences in density between water and grease. Grease is less dense, so it naturally rises to the top.

Cleaning and Maintenance

You should know that regular maintenance and cleaning are necessary to maintain your system. Not cleaning your grease trap can cause clogs and backups, defeating the trap’s entire purpose. Routine checks and cleanings keep the trap functional and your plumbing system running smoothly.

Types of Grease Traps

There are various types of grease traps, and each has a different design to suit different needs and environments. Knowing the differences helps you choose one that works with your setup.

Passive Grease Traps

These are the most common and simplest types. They work by slowing wastewater flow so FOG can separate and rise to the top. These traps are popular because they’re cost-effective and easy to install. However, they require frequent manual cleaning and stop working if you don’t properly maintain them.

Automatic Grease Traps

These traps have a motorized system that automatically skims and removes grease. The result is less manual cleaning. People love them because they require less maintenance. The problem is they also cost more and require regular checks to keep the mechanical parts functioning.

Gravity Grease Traps

Ideal for larger establishments, these traps use gravity to separate FOG from water in a larger chamber. They do an excellent job of handling high volumes of wastewater and have low maintenance requirements. They need more space and have a higher upfront installation cost, though, so you’ll typically only see them in commercial settings.

Each type of grease trap has strengths and weaknesses, but all play an integral role in keeping your plumbing system running smoothly. As a result, you’ll want to choose wisely based on your needs, budget, and available space.

Common Issues with Grease Traps

You’ll likely encounter numerous problems with your grease traps if you don’t maintain them. Common issues include:

Clogging

Clogging occurs when FOG and solid waste accumulate and restrict wastewater flow. You might get to this stage because of irregular cleaning schedules or overloading the trap beyond its capacity. Regular maintenance and not overfilling the trap can help prevent this problem.

Overflow

Your grease trap can overflow when you neglect it. You might also run into this issue if there’s a problem with the installation. This scenario can cause grease-laden water to spill over and cause blockages downstream. Confirming the trap is the right size and taking the time to empty it periodically reduces this risk.

Foul Odors

A grease and organic waste build-up in the trap can produce unpleasant smells. These odors are often due to bacteria thriving in the stagnant FOG layer. Proper cleaning and using enzyme-based treatments can help keep the odors at bay.

Your grease trap’s performance is dependent on proper installation and regular maintenance. Keeping up with these tasks prolongs the life of the trap and creates a clean and odor-free environment.

Grease Trap Cleaning and Maintenance

Book an Appointment With Sanitary Plumbing

Grease traps can do all kinds of good in the multifamilies you manage by reducing sewer system clogs. However, you’ll need to maintain the traps and the rest of your plumbing system to minimize the issues you encounter. Sanitary Plumbing can assist with our drain and sewer cleaning services. Call us at 212.734.5000 to schedule an appointment or book a maintenance subscription online.