Plumbing 101 – Why Use a Grease Trap?

Why use a grease trap?

The use of Grease Traps or Grease Separators is largely dictated by local or municipal codes however regardless of the code using them it is good for your sewer system. Before we explain how grease traps work it’s probably a good time to explain what they actually do. A grease trap is appurtenance designed to capture grease, fats and oils before they enter the sanitary system.

Where should Grease Traps be Used?

A grease trap should always be used to prevent grease from getting into the sewer lines in any school, restaurant, hotel, hospital or pretty much any building that has the facilities to prepare food en mass. Grease interceptors should also be used in dairies, food processing plants, meat packing facilities where fats and greases are a by-product of the processes.

Reasons to Install a Grease Separators

  • Grease adheres to the inside of sewer lines slowly choking off flow. Grease traps catch the grease before it has a chance to make a mess of things like sewer back ups and costly repairs.


  • If grease isn’t treated it can make it’s way to our rivers and lakes. We don’t have to explain how that would effect the ecosystem.


  • Grease impedes bacterial breakdown in septic tanks and sewage disposal facilities.

So How Do They Work?

Why use a grease trap?As the water drains into the interceptor it passes a flow restrictor . (Most grease traps are equipped with a flow control device but some are not. The plumbing contractor would then be responsible for the flow control device). The flow control device slows things down so the interceptor can do it’s thing. The water then passes through a series of removable baffles that aids in separating greases, fats and oils. Once the grease is separated it floats to the top where it accumulates. When the grease trap no longer functions efficiently the top should be removed and the grease should be cleaned out and disposed of safely. Believe it or not grease traps can remove between 80% and 90% of contaminating greases.

Some Tips on Grease Trap Installation

  • A grease interceptor should be installed as close as possible to the fixture or fixtures it serves. Because the waste water is usually quite warm it aids in grease separation.


  • Grease traps can be installed above the ground serving multiple fixtures.


  • Grease traps can be installed above the ground serving a single fixture.


  • Grease traps can be installed fully recessed serving multiple fixtures.


  • Grease traps can be installed fully recessed for a single fixture application.


  • Grease traps can also be installed fully recessed beneath the finished floor with an extension to get it up to the finished floor.

There are Other Interceptors Designed to Help Your Sewer Lines

The grease interceptor isn’t the only trap that you can use to protect your drainage system. Grease traps are not design to capture solid materials. In a restaurant or cafeteria application in addition to grease waste you also get solids from food scraps. Grease attracts solids so you end up with grease cakes (yummy!!) that promote decay leading to pretty foul odors. As you can imagine under these conditions pipes can become blocked and the grease trap itself can become filled with debris.

Here some of the other interceptors available:

  1. Sand Interceptor
  2. Lint Interceptor
  3. Oil/Sediment Interceptor – These are used and most times required whenever oils are used or present in the work environment i.e. service stations, car washes, garages, dry cleaners, industrial plants, auto repair garages, machine shops etc. Capturing these volatile and flammable oils before they can contaminate the sewer system is essential to prevent potential fires and explosions. In the situations listed above sediment can also be an issue therefore most oil interceptors are also equipped with sediment buckets to capture small debris.
  4. Hair Interceptor –  As you can imagine this is used in barber shops, hair salons, veterinarian clinics and pet grooming facilities  to catch the hair before it gets into the waste piping. Hair is one of the biggest culprits for local clogging in a sewer line, having an interceptor to eliminate the problem is essential. Cleaning them out isn’t all that much fun so call a professional to do the dirty work.

Thanks for reading and if you have any questions regarding Interceptors please don’t hesitate to leave us a reply.

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