How Does a Grease Trap Work?
There are a lot of moving parts in a commercial kitchen. But one of the most important is the grease trap. A kitchen grease trap helps restaurants and food service businesses stay compliant and prevent grease backups. How does a grease trap work? In this article, we’ll cover that and more so you can better understand their importance in the kitchen.
What Is a Grease Trap?
A grease trap (also called a grease interceptor) captures fats, oils, and grease (FOG) before they enter the wastewater system. If your kitchen doesn’t have one and you just throw all your grease down the drain, it can clog pipes and cause major sewer system damage.
Grease traps are required in many commercial kitchens to meet local plumbing codes and environmental standards. They’re a key part of grease trap plumbing systems in restaurants, cafeterias, and food production facilities.
How a Grease Trap Works (Step-by-Step)
So, how do grease traps work? It all comes down to flow, separation, and accumulation. Here’s the step-by-step process:
- Wastewater from sinks and dishwashers flows down the drain and into the grease trap.
- The trap slows the flow of water, allowing time for the contents to cool and separate.
- FOGs rise to the top, since they’re lighter than water.
- Solids settle at the bottom, while cleaner water flows out of the tank into the main sewage line.
- The FOG layer accumulates over time and must be professionally cleaned to avoid blockages and overflows.
Grease Trap Diagram and Tank Design Overview
Grease traps come in various sizes and designs, but the three most common kinds of grease traps for kitchens include:
- Passive grease trap: These are plumbing devices found under sinks with three compartments. They’re smaller and better for at-home kitchens.
- Grease recovery device: These remove grease automatically once it's trapped. Grease can then be collected and recycled with waste vegetable oil collected from a deep fryer.
- In-ground grease trap: These devices not only capture grease, but also oil, sediment, and lint, among other solids. A grease trap in the ground is larger and typically a better choice for large restaurants and even hospitals or school cafeterias.
What does a grease trap look like? You can better understand how a grease trap works by taking a look at this diagram:
In this grease trap diagram, you’ll see two chambers inside the unit—one for intake and separation, and one for outflow. Baffles help slow water and guide grease to the top. This grease tank design keeps grease from entering the sewer, and it’s easy to maintain.
Why Grease Traps Are Critical for Commercial Kitchens
Without a functioning grease trap, grease buildup can lead to:
- Drain backups and foul odors
- Sewer line blockages
- Health violations or shutdowns
- Expensive emergency plumbing repairs
Clean traps are especially important in food service. That’s why professional grease trap service is such a big deal—it can help you remain compliant and keep your plumbing interceptors in great shape.
FAQs About Grease Trap Function and Maintenance
How do I know if my grease trap is full?
Your grease trap might be full if it’s slow to drain, clogs frequently, or smells rancid.
Does a grease trap always have water in it?
Yes. A properly functioning trap always contains water. The water layer helps maintain the separation between FOG, solids, and outflow.
Can I use a grease trap in a home kitchen?
Small grease traps for kitchens are available. They can be especially useful for people who cook a lot of fatty or fried foods so they don’t end up pouring grease or oil down the drain.
Are grease traps required by law in restaurants?
Local plumbing codes often require restaurants and food service facilities to install grease interceptors and maintain them regularly. Failure to comply can lead to fines or business closures.
Where does the grease from a grease trap go?
Typically, you’ll need to call a waste contractor to haul away your grease. It may be processed for biofuel, composted, or disposed of at an approved facility.
When to Call a Professional for Grease Trap Help
DIY plumbing in your home is one thing, but it’s typically not recommended when your facilities are going to be inspected. One small mistake could set you back from opening on schedule.
A commercial plumber can help with everything from grease trap installation to full-service cleanouts. If you’ve noticed bad smells, slow drains, or mystery leaks, don’t wait for a shutdown. Call Roto-Rooter today to schedule expert grease trap service and keep your kitchen running clean, safe, and compliant.