What is a Grease Trap?

What is a grease trap?

Simply put, a grease trap is a receptacle that kitchen wastewater flows through before entering the sanitary sewer lines. This receptacle — technically defined as a grease interceptor — interceptors, captures, or "traps" grease. How?

Grease, the industry term for animal fats and vegetable oils, is 10 to 15 percent less dense than water. Grease also won't mix with water. As a result, fats and oils float on top of water.

When kitchen wastewater flows through a grease interceptor, the grease and oils rise to the surface inside the trap and are trapped using a system of baffles. The captured grease and oils fill the trap from the top down, displacing “clean” water out of the bottom of the trap and into sewer line.

Peer into a grease trap and youll see a mat of grease. When this mat of grease gets deep enough, the trap must be cleaned out.

Types of grease traps

In the United States, there are three major types of grease traps found in food service establishments:

  • Small passive hydromechanical grease interceptors (also known as grease traps)
  • Large pre-cast concrete gravity grease interceptors
  • Automatic grease/oil removal systems such as Big Dipper

Passive grease traps date back to 1885 when the first U.S. patent was issued. Today's large and small grease traps use the same basic operating design as the 1885 model. While they do a fine job trapping grease, removing the grease is a task left to the owner.

Small passive traps must be cleaned out by hand. Large pre-cast traps, on the other hand, must be cleaned out by a professionally operated vacuum or pump truck.

Grease trap efficiency

As grease traps of the traditional design fill with grease, their efficiency at separating grease from wastewater decreases. When a trap is filled to capacity with fats and oil, separation no longer occurs and the trap no longer functions properly.

Traditional concrete traps must be pumped out after just 25 percent of their volume is filled, because after that they no longer work well enough to keep fats and oils out of the sewage systems.

Compact, high-capacity interceptors, such as Thermaco's Trapzilla systems, are engineered so they never lose efficiency. They can hold upwards of 90 percent of their volume in grease before they must be cleaned out.

If traditionally designed passive traps are not cleaned out on a timely basis, they begin to allow too much grease into the sewer system, where it can cause blockages and sewage backups. This creates problems for wastewater system operators as well as the food service establishment.

Improperly maintained grease traps (or the failure to install a grease trap when required) often leads to fines, down-time, and can lead to bad publicity.

Automatic systems

Big Dipper systems work a bit differently than traditional traps. In them, grease is skimmed out automatically on a programmed schedule based on the amount of grease produced.

This automation means employees don't have to measure or check grease levels. The grease in these automatic systems accumulates in a separate chamber and is simply disposed of in a municipally approved waste container.

Learn more about Thermaco's products and how they outperform traditional grease traps and interceptors.