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How to Install and Clean a Grease Trap (for Your Home)

A photo collage of a grease traps.

Cooking with grease can be messy. If left unchecked, this accumulation of waste can not only turn out to be an expensive process to undo but can also become extremely gross.

Even worse, grease can clog sewer lines within the neighborhood and create problems at local water treatment facilities. Therefore, it is a bad idea to pour fats, oils, and grease down the kitchen drain.

To help mitigate any issues arising from clogged sewer lines you need a grease trap.

What is a grease trap?

Simply put, a grease trap (also commonly known as a grease converter, grease recovery device, and grease interceptor) is a plumbing fixture designed to intercept most solids and greases before entering the sewer waste system.

Capacity ranges from 35 liters to 45,000 liters and can be constructed from many different materials, including cast iron, concrete, plastics, and stainless steel. The grease traps can be located in areas such as inside and outside the kitchen, and above and below ground.

Benefits of having a Grease Trap in Your Home

Needless to say, a grease trap is an invaluable addition to any working kitchen. If you’re an avid cook and are constantly flushing grease down your sink, you’re definitely going to want to read about the following benefits: It is not only beneficial to the environment but also financially.

1. Environmentally friendly

A grease trap being installed outdoor with the grasses.

Grease traps help keep the environment clean by reducing pollution. When you cook without a grease trap the fats, oils, and grease (FOG) flow into local streams and rivers.

FOG can become toxic over time. A grease trap intercepts the FOG before it reaches your sewage system. In addition, the FOG can be converted into rich agricultural mulch that can be used on farms as a fertilizer.

2. Economically Beneficial

Having grease traps installed will greatly reduce the expensive repairs and maintenance that accrue from blocked pipes. As long as a grease trap is properly maintained, you won’t have to worry about having a blocked sewer system. Additionally, maintaining a grease trap is hassle-free. They’re quite easy to clean.

Grease Trap Sizing

Grease traps come in a variety of sizes, from individual kitchen models to ones large enough to be fitted in big eateries and restaurants. For residential grease traps, we highly recommend hiring the services of a professional so as to ascertain the right size for your needs.

How does a grease interceptor work?

A three compartment grease interceptor.

A grease trap works by cooling warm or hot greasy water. Vegetable oils and animal fats are 10 to 15% less dense than water and are insoluble in water. By allowing the fats, oils, and grease to cool, the different layers of the mixture are able to separate into individual layers for easy separation.

Since the FOG is lighter in density, it is able to float on top, and the water beneath is left to continue flowing down the drain. The floating FOG is then trapped by a grease trap.

Over time, grease and solids build up, and if the accumulation is left unchecked for a long, can block the inlet. As such, grease traps need to be pumped/cleaned out on a regular basis.

Below is an illustration of how a grease trap works:

Illustration of how a grease trap works

Types of Grease Traps

There are three different types of grease traps; gravity, automatic, and passive hydromechanical (manual). The former two are mainly used for large installations like restaurants or hotels, while the passive hydromechanical grease trap is used in homes.

We’re going to focus on residential grease traps but if you would like more information on commercial grease traps check out this article.

The passive hydromechanical (manual) grease trap is a traditional passive system commonly used in smaller establishments, including homes. They’re smaller, point-of-use units installed beside kitchen dishwashers or used under three-compartment sinks. There’re preferred due to their small initial investment and maintenance costs.

Naturally, the passive hydromechanical grease trap has up to 100gpm handling capacity. Any waste exceeding this maximum allowable flow should be left to either the automatic grease receptor or the gravity receptor as they allow for more handling capacity.

Manual grease trap designs date back to the Victorian days. Nathaniel Whiting was the first person to obtain a patent for a grease trap. Grease traps are usually constructed from stainless steel or plastic and must be cleaned occasionally.

How To Install A Residential Grease Trap

Unless you lack basic skills, grease trap installation doesn’t require the services of a professional plumber. A grease trap should be accessible so you can clean it out when it fills up, but the frequency is much lower in homes than in commercial establishments.

Here are the steps to follow in grease trap installation:

1. Determine where to install the grease trap

A close up photo of a grease trap.

The most convenient place to install a grease trap is beneath your sink but it can also be installed outside your home. Unless your home has several sinks that are regularly used for cooking, setting it up beneath your sink is recommended.

2. Connect the grease trap

Read the manufacturer’s manual for instructions. While installation may vary from one model to another, most grease traps have three connections.

The first connection connects to the sink or the wastewater source.

The second connection is designed to connect to the holding tank vent. It is however recommended by plumbers to install a cleanout tee before connecting the device to it.

Lastly, the third connection is usually found on the lower right of the grease trap. It is mostly secured to the pipe that leads to the sewage system.

In order to help the grease trap work even more efficiently and last longer between cleanings, it is recommended that you pour hot water on any food or greasy liquid going down the drain.

How To Clean A Residential Grease Trap

This section is intended to help homeowners who have a residential kitchen grease trap with some bits of general information. Before embarking on the process, you’ll need the following items:

  • Oil dry (you can buy it at an auto supply store)
  • 2 or 3 trash can liners (garbage bags)
  • large trash can
  • Proper tools to open trap
  • Paper towels
  • A wooden dowel for measuring
  • Tools for removing contents (scraper and scoop)
  • Rubber gloves

To begin, you’ll need to:

  • Make sure the work area is well prepared
  • Ensure the trash can liners are put into the trash can
  • Add some oil dry. This is essential as it soaks up all the liquid thereby making transportation a breeze.

Now that everything is set, let’s begin the steps required to clean a grease trap.

 1. Detach the lid from the grease trap gently using the pry bar

A zoom in photo of a grease trap lid being opened,

Under the cover, you’ll notice that there are gaskets. It’s imperative that you go slowly throughout the process of detaching the lid from the grease trap. Any damage and you’ll need to replace your gaskets.

2. Inspect The Grease Trap

During the cleaning process, you need to be aware of where parts are located and how to install them back safely without damaging them. Plumbers recommend that you have a drawing of the interior so that you have a point of reference.

3. Insert a Measuring Stick

In order to measure how full the grease trap is you need to insert a measuring stick.

Lower it gently and stir lightly so that the debris clearly marks the level. The next step is to remove the measuring stick and record the results in a fat, oils, and grease pump-out report.

4. Remove any still water using a small bucket

Better still, you can keep the water in a large bucket, and pour it back into the drainage after you’re finished with waste collection.

5. Use a scraper and scoop to remove waste from your grease trap

A close up photo of a man scooping a waste from his grease trap.

Remove all solid waste from the grease interceptor. For easier transportation of the waste, you can mix it with oil dry, which solidifies any liquids, including water. Then place the mixture into a heavy-duty plastic trash bag for transportation.

6. Clean the trap sides, lids, and parts

Using a pot scrubber with soap and room temperature water, remove excess waste from the lid and trap sides.

Next, use water to flush the parts and screens in order to get rid of debris and soap.

7. Reinstall the grease trap

Now that your grease trap is cleaned out, it’s time to reinstall it. You can use the drawing of the great trap as a point of reference.