What Are Grease Traps and How do they work?

Cooking for a large number of people can be a difficult thing to handle, especially if you’re making two or more dishes at the same time. 

You often can’t waste time carefully scooping used fat and grease into the garbage, so dumping it in the sink is the quickest option. But, this can eventually lead to clogs. Fortunately, there is a way to reduce the chance of greasy food clogs from your kitchen’s drain pipes. No one wants to unclog the slimy clump of grease and food bits, so grease traps are the next best option!

When a problem happens with the town’s sewer system, water companies look for the root of the cause in the buildings surrounding the issue. After identifying which building caused it, the local water company will charge the owner with a heavy fine. This worry can easily be prevented by investing in a grease trap for your kitchen. 

Yet, few people can provide an answer to the question of “what is a grease trap and how does it work”. To help provide you with the information you need on grease traps, we’ve detailed expert plumber advice on what they are and how they work below.

What are grease traps?

If you have ever worked in a restaurant kitchen or cooked at home, you have probably seen someone get rid of the excess oil and melted fats by pouring them into a sink. 

While that may seem better than dumping it straight into the trash, all the grease and fat can thicken over time. Eventually, the grease can build up and form a clog in your pipes, causing costly amounts of damage.

Grease traps are parts that have been specifically made to filter out any fat, oil and grease (FOG) from the wastewater that goes down your drain pipe. Also known as grease interceptors, converters, FOG traps etc., grease traps have been used to help clean water for over a century. 

Today, many countries around the world use them to protect their sewer lines and prevent FOG-related clogs.

How do grease traps work?

Grease traps often come in one of two forms, manual or automatic. Let’s break down how grease traps work. Despite the different types, both manual and automatic grease traps work fairly similarly. Wastewater enters the trap, where it’s separated into solids, FOG and the wastewater itself. The food and grease are then removed before the rest is sent through the sewers.

The difference between the two is that manual grease traps, though much cheaper to install, need the food and grease to be cleaned out by a professional. Automatic grease traps do the same thing as manual traps but on a set schedule.

What does a grease trap look like?

Grease traps, both manual and automatic, are shaped like a large tub. When it comes to the more commonly found manual grease traps, a simple connection is made between the kitchen sink’s drainage system and the trap, where a removable strainer is fitted in. 

As mentioned, water comes into the system, where it’s run through the strainers to trap the FOG. In many models, the grease trap will also filter out solids, leaving only the water to be treated.

In automatic grease traps, more pipes are installed to pull the grease away from the water, though the shape remains the same. When the wastewater comes in, it’s separated as usual, but the additional pipes allow the system to draw the FOG away on its own. The cleaner water is then sent out, and any lingering solids or grease is cleaned out with another pipe.

So, what are grease traps again? Simply put, a grease trap is a large system that cleans and separates the grease and solid food from the cleaner wastewater before sending it into the drain system

Who needs a grease trap?

Typically, grease traps are used in large restaurants, and commercial buildings where a lot of food is cooked and grease is quickly disposed of. You can still install a grease trap in a home or a business, but they have far more use in commercial buildings that see a lot of food waste and grease going down the drains.

Besides restaurants, grease traps are a great idea for bars, cafes, bakeries, schools and residential buildings that house many people, like hotels and condos. If the grease that the residents of the building dispose of is a lot, your business will have to follow specific maintenance codes to run. A grease trap will still be a perfect solution to prevent clogs.

How much do grease traps cost?

The cost of a grease trap and its installation can change depending on the model and whether it’s automatic or manual. On average, can range between $250 to $1000, with newer, and automatic traps naturally costing more. 

Grease trap maintenance is another cost you’ll need to consider. Typically, this fall between the $120 to $300 range, depending on the size of your business and plumbing system. A grease trap will require the assistance of a professional, so factoring in the cost of maintenance is essential. 

Your grease trap will need to be replaced every 5 to 10 years on average when it reaches the end of its lifespan. This will cost another $250 at least. Taking care of your grease trap and getting it serviced regularly will keep it working for a long time, ensuring the required but useful system runs for its full lifespan.


“What are grease traps” is a simple question to answer. Grease traps are a special but mandatory system used by food service businesses and schools to remove the food, oil and grease from the wastewater. There are rules and regulations that these businesses must follow to avoid fines and any costly damage to their own sewer pipes or the local sewers. 

While helpful at maintaining wastewater regulations, grease traps can also be quite helpful to the workers themselves. No one likes to unclog a greasy kitchen sink, and with the help of a grease trap, they don’t have to.

Looking to install a grease trap? We can help. Contact us to book an appointment today.

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