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What Are Grease Traps for Commercial Kitchens and How to Clean Them

grease traps for restaurants

As global awareness of environmental concerns continues to grow, examining your FOG (Fats, Oils, and Grease) management presently can be a prudent investment, safeguarding your business against anticipated, increasingly stringent global legislation in the future. Grease traps are the central collection point for all fats, oils, and grease (FOGs). Neglecting their cleaning not only exposes you to regulatory consequences but also subjects you to substantial fines. This article covers everything related to grease traps for commercial kitchens: definition, types, and how to clean them. Keep reading to learn more about FOG management.

What Are Grease Traps for Commercial Kitchens

Whether positioned above or below ground level, a grease traps for commercial kitchens function as an interceptor, arrestor, tank, or pit. Its primary role involves facilitating the cooling and separation of grease from wastewater. The discharge of fat, oil, and grease from food-related establishments significantly contributes to blockages within the municipal sewerage system. In the absence of a suitably sized and well-maintained grease trap, grease can infiltrate the sewer lines, resulting in accumulation. This build-up leads to encrustation, impeding the smooth flow of wastewater within the sewers and potentially causing overflow into your premises or other public areas.
All food-handling establishments, such as restaurants, coffee shops, and hawker centres, must incorporate grease traps as a mandatory requirement.

How Does a Grease Trap Work

portable grease trap
Animal fats and vegetable oils, also known as grease, have a lower density than water by approximately 10 to 15 percent. As a result, grease does not mix with water; instead, it floats on top of it. This is the principle that grease traps utilise to function effectively.
When wastewater flows into a grease trap, it experiences a decrease in flow rate, allowing the liquid adequate time to cool and segregate into distinct layers. The trapped grease is collected at the top of the interceptor using a system of baffles. Meanwhile, solids settle at the bottom, and the separated clear water is released through an outlet baffle. Many grease traps also feature strainers for collecting solid debris to reduce the amount of solids that accumulate at the bottom of the trap.
Over a period of time, solids and grease tend to accumulate in the trap. If this build-up is not taken care of, it may overflow through the outlet and, in certain circumstances, even back up through the inlet. Therefore, it is highly recommended to clean or pump out the trap periodically.
To determine when to clean or pump out your grease trap, you should consider the amount of wastewater produced and the size of the trap. Typically, this should be done every 2-4 weeks, but you can extend this to 8 weeks by adding a biological grease treatment fluid to your system. This fluid contains non-pathogenic bacteria, nutrients, and enzymes that break down FOG and improve the performance of your grease trap. This process is called “dosing.”
Dosing can also be applied at the outlet stage to prevent fats, oils, and grease (FOG) build-up in internal piping as an additional method.


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Types of Grease Traps for Commercial Kitchens

Three categories of grease traps include passive hydromechanical (manual), automatic, and gravity-based systems.

Passive Hydromechanical (Manual) Grease Traps

grease trap singapore passive hydromechanical (manual)
Many smaller establishments prefer traditional passive systems as they are affordable and come in different sizes to fit under most sinks. These systems are commonly used due to their low initial investment cost and ability to handle smaller wastewater production needs. Larger units are also available to accommodate bigger requirements.
The earliest known design for manual grease traps dates back to 1885, which is also the year when the first U.S. patent for the same was issued. Interestingly, the basic operating design of grease interceptors has remained largely unchanged since the 1885 model. Typically, these interceptors are made of either plastic or stainless steel and require manual cleaning regularly.

Automatic Grease Traps

grease trap construction automatic grease traps
Automatic systems, called AGRUs (Automatic Grease Removal Units), employ principles similar to conventional passive traps. However, they automatically reheat and remove FOG (Fats, Oils, and Grease) according to a pre-set schedule. The extracted FOG is subsequently transferred into a collection bin for convenient removal and recycling. This programmed schedule adapts to the quantity of FOG generated, eliminating the need for operators to monitor or measure grease levels manually.
Like passive systems, they come in various sizes to suit diverse needs. Despite having a higher upfront investment, they are more effective, with reduced long-term operational and maintenance expenses.

Gravity Grease Traps

gravity grease trap external grease trap
Gravity systems typically consist of expansive subterranean tanks made from materials such as concrete, fibreglass, or steel. They function like passive hydro mechanical traps but boast significantly greater capacity, making them more suitable for high-flow scenarios.
Regular maintenance of gravity traps involves scheduled pumping, a task commonly performed by specialised grease management service companies.

Cleaning the Grease Trap

Although cleaning grease traps may be an unpleasant task, it remains essential. The Environmental Protection Agency (EPA) reports that 47% of reported blockages in sewage systems are caused by FOG release. Regularly maintaining your trap can prevent your contribution to this issue and lower the chances of costly plumbing problems. Moreover, it eliminates unpleasant odours caused by accumulated FOG. Neglecting grease trap maintenance could lead to regulatory penalties and potential business closures due to violations of relevant laws and regulations.

Grease build-up serves as a significant cause of fires in restaurants. Neglecting the adequate cleaning and maintenance of your restaurant’s grease traps may result in fires, leading to substantial financial losses of thousands of dollars and hampering business operations.

Necessary Items

To ensure your safety and make the job easier, gathering the right gear before starting is essential. Rubber gloves will protect your hands, while a mask or nose plug will help you defend against odours. Protective coveralls are also important, along with a crowbar and wrench to lift the lid off of the grease trap. Additionally, you will need a scraper, a steel pot scrubber, dish soap, and a shop vacuum.

Locate and Assess

Locate the grease trap on the food establishment’s premises, which can be found either indoors or outdoors. Outdoor traps might be distinguished by their manhole coverings or septic tank-like designs. If situated indoors, the grease trap can typically be found in the restaurant’s basement (directly below the kitchen), beneath the kitchen sink, or concealed under a metal flashing in the kitchen flooring.
Once you’ve identified the grease trap, assess its physical dimensions. Examining the tank’s capacity will help determine whether professional assistance is needed or if it can be cleaned by authorised restaurant staff. Grease traps ranging between 500 and 2500 gallons typically require professional equipment and training, while smaller traps may be cleaned by permitted restaurant personnel.

Guidelines for Cleaning Grease Traps

what kind of grease trap should I install
Allow the fats, oils and grease to float to the top by using cool water. After releasing the hot wastewater from the dishwasher or sink, wait at least ten minutes for it to cool down.
Pry off the grease tank cover to access the fats, oils, and greases. The cover is held in place by a delicate and essential part called the gasket, which can easily be damaged if not handled carefully. Therefore, it is crucial to use precautionary measures when attempting to lift off the cover.
The crowbar proves helpful here unless the grease trap cover is secured with bolts. If the grease trap has a moulded plastic lid, it will be easier as it can be easily snapped off.
You will see a two-inch thick accumulation of grease sludge. Use a scoop to eliminate the floating FOGs. After extracting the fats, oils, and greases from the tank, water and residual food solids will remain.
A powerful shop vacuum can help eliminate the remaining solid particles and water. Ensure the automatic dishwasher is switched off and the sinks remain inactive to avoid the continuous filling of the grease trap while you work.
The most important and arduous task is complete. Now, proceed to clean the trap’s baffles, sides, and lid by scraping them. Use the shop vacuum to remove any solidified grease particles stuck in the trap’s crevices. For a thorough cleaning, employ the shop vacuum to eliminate any remaining FOGs (Fats, Oils, Greases) from the grease trap.
Afterwards, use elbow grease, a steel pot scrubber, dish soap, and tepid water to eliminate unpleasant odours from the tank. Ensure the grease trap’s baffles, sides, and lid are thoroughly scrubbed.


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Rinse the soap and debris thoroughly several times using fresh water. This will result in a clean grease trap, which should be maintained every four to six weeks.

After completing the most strenuous aspect of the task:

  1. Assess your handiwork.
  2. Ensure that the grease trap is entirely free of FOGs and that there are no blockages impeding smooth water drainage.
  3. Proceed by draining a gallon of clean water from the kitchen sink.

Ensure unobstructed water flow through the grease trap. If a blockage is present, seek assistance from a licensed plumber to resolve it. Reassemble the components of the grease trap, such as the baffle and lid.


grease trap waste disposal

Ensure appropriate disposal of accumulated fats, oils, and greases by placing them in double-lined garbage bags. If the quantity of FOGs is minimal, deposit them in the local dumpster. A pro-tip is to combine FOGs from the shop vacuum with kitty litter to solidify the grease particles before disposal. For substantial amounts of grease trap sludge, it is advisable to engage professional grease trap companies for proper disposal.

Things to Keep In Mind

Regular maintenance of grease traps is essential, ideally scheduling cleanings every four to six weeks. To extend the duration between cleanings, using bacteria additives (such as enzymatic cleaners) that naturally decompose waste can be beneficial. However, caution is advised against using hot water flushes or products containing only enzymes. These can liquefy FOGs (Fats, Oils, Grease), allowing them to flow into municipal sewer lines, causing potential issues. So, make sure your enzyme cleaner has a good mixture of enzymes and surfactants.

Conclusion: Grease Traps for Commercial Kitchens

In conclusion, proactive FOG (Fats, Oils, and Grease) management via grease traps is vital for food-related businesses amidst increasing environmental concerns and stringent regulations. From passive to automatic and gravity-based systems, Grease traps offer tailored solutions for diverse establishments. Regular maintenance, proper disposal, and use of recommended products like Drain Guard are crucial for preventing blockages, environmental hazards, and regulatory penalties. Adhering to maintenance schedules and employing enzymatic cleaners responsibly facilitates effective FOG control. Prioritising grease trap upkeep ensures compliance and mitigates operational disruptions, fostering sustainable business practices and environmental responsibility.

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