What is a Grease Trap?

Mary McMahon
Mary McMahon

A grease trap, sometimes called a grease interceptor, is a piece of restaurant equipment that is required in many regions to keep the sewers functional. It acts as a filter to remove fats and oils from water before it enters the municipal waste system. Since fats and oils can clog a sewer system, the use of a trap ensures that the sewer system runs smoothly. In a commercial kitchen, it treats all of the water coming out of the kitchen.

Grease traps are required in many restaurants.
Grease traps are required in many restaurants.

A properly equipped commercial kitchen usually has multiple sinks at prep stations, an industrial dishwasher, and large sinks for pre-treatment of dishes and other cooking tasks. The floors typically are sloped with central drains, allowing workers to clean the whole kitchen, and it may also have an in-house laundry facility. The combined drainage from all of these sources can be formidable, requiring a very large grease trap to ensure that water will drain smoothly.

Efficiency will be lost in a restaurant if a grease trap is not cleaned regularly.
Efficiency will be lost in a restaurant if a grease trap is not cleaned regularly.

A grease trap looks like a large box or barrel spliced into the water drainage line. When the water enters the trap, it cools down, allowing the lighter oil to precipitate out to the top. A series of baffles collect oil and chunks of material while the water sinks to the bottom. An exit pipe at the base of the device allows the treated water to flow out, while the grease remains enclosed on top.

In order to function properly, a grease trap and its lines must be regularly cleaned and maintained. Staff can empty it by hand, or a company may be hired to pump out the grease. Some use automatic systems to skim out the grease and dump it into a container, but these still need to be periodically broken down and cleaned. All of the baffles of a grease trap should be scrubbed, and the drainage lines should be scoured to remove accumulated grease.

Efficiency will be lost if a grease trap is not cleaned regularly. Ultimately, it can clog, leading to backups of water into the kitchen. A cleaning rotation and log for the trap is usually kept, to ensure that it is kept operating in peak condition. Health inspectors may periodically check it as well, to assure themselves that it is working properly, and that all of the water in the establishment is being treated before draining into the sewer.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Nowadays,some of the regions in China are following the government's guidance to install an automatic grease trap in their own kitchens and restaurants because of the common sewer-clogging problem, and we are actually the provider. We believe that as people are gradually interested in environmental protection, our product can be a great help to make earth a better place.


To ensure efficiency of grease trap it should be well-maintained, it's very important in all commercial kitchen to prevent any environmental problem.


A Zurn grease trap can have pitch and height adjustments (a more recent innovation) so a restaurant doesn't have to worry about needing a grease trap installation repair - it can be adjusted. When an installation is done well, you'll avoid water pooling around the drain and increase the efficiency of your grease trap.


Cleaning a greasetrap sounds like a totally disgusting job, I'd vote for the automatic system any day! But it certainly is something that needs to be done, any I think that restaurant that doesn't keep this well-maintained should be fined or closed down.

Now that it's been shown that grease can fuel some cars, maybe it will be less of a problem, what do you think? Cooking oil in the car instead of down the drain!

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