What Is a Grease Trap and How Does it Work?

What Is Grease Trap?

A grease trap, also known as a grease interceptor, is a plumbing device used in restaurant and food service kitchens to remove grease from wastewater.

It is designed to prevent oils and greases from overwhelming septic tanks or treatment facilities, which could result in the release of untreated sewage into the environment.

Grease traps have been in use since the late 1800s and come in various sizes and materials.

The most common types are specified by ASME and are required to remove at least 90% of fats, oils, and greases (FOGs).

Grease traps work by allowing solids to settle in the tank while the grease-free water is discharged.

However, regular maintenance and cleaning are necessary to prevent issues and ensure proper functioning.

Key Points:

  • Grease traps are used in restaurant and food service kitchens to remove grease from wastewater
  • They prevent oils and greases from overwhelming septic tanks or treatment facilities
  • Grease traps have been used since the late 1800s and come in various sizes and materials
  • ASME specifies the most common types of grease traps that are required to remove at least 90% of fats, oils, and greases (FOGs)
  • Grease traps allow solids to settle in the tank while discharging grease-free water
  • Regular maintenance and cleaning are necessary for proper functioning of grease traps

Did You Know?

1. The concept of grease traps dates back to ancient Rome, where the sewage system included similar devices to remove fats and oils from waste water before it overflowed into the rivers.

2. Grease traps are not only utilized in restaurants and commercial kitchens but are also commonly found in households to prevent pipe blockages caused by fats, oils, and grease (FOG) residues.

3. The material from which grease traps are made has evolved throughout history. In the past, grease traps were often constructed from rubble or bricks, whereas modern ones are typically made of durable materials like stainless steel or cast iron.

4. Some grease traps are designed to automatically skim and separate the grease layer from the water, reducing the need for manual cleaning and maintenance.

5. Grease traps are not only effective in trapping fats, oils, and grease, but they can also help in capturing solids suspended in wastewater, such as food particles, preventing them from clogging the drain pipes.

What Is A Grease Trap?

A grease trap, also known as a grease interceptor, is a device used in restaurant and food service kitchens to remove grease from wastewater.

Grease traps are necessary because the oils and greases produced during cooking and food preparation can easily accumulate in the plumbing system, leading to blockages and backups.

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These traps work by intercepting and separating the grease from the water, allowing the grease-free water to flow out while trapping the grease inside the device.

Grease traps have been in use since the late 1800s and have become a standard fixture in commercial kitchens. They are typically installed between the kitchen sinks and the septic tanks or sewage treatment facilities.

When wastewater flows into the grease trap, it first passes through a baffled inlet, which helps to direct the flow and slow it down to allow for better separation of solids and grease.

The wastewater then moves through a series of compartments or chambers, where the grease rises to the top and solids settle at the bottom, leaving the grease-free water in the middle to exit the trap.

Importance And Function Of Grease Traps

The importance of grease traps cannot be overstated in restaurant and food service kitchens. Without these devices, the excessive grease and oils produced during cooking would overwhelm the septic tanks or sewage treatment facilities, leading to clogs, backups, and potential environmental hazards.

Grease traps play a crucial role in preventing untreated sewage from being released into the environment.

The function of a grease trap is to effectively separate and capture fats, oils, and greases (FOGs) from the wastewater. Grease, being lighter than water, naturally rises to the top of the trap. The trapped grease is then contained within the device until it is manually pumped out and properly disposed of.

By removing the majority of the grease from the wastewater, grease traps help prevent clogs in the plumbing system and reduce the load on the septic tanks or treatment facilities.

Different Types Of Grease Trap Devices

There are three primary types of grease trap devices used in commercial kitchens, each with its own advantages and applications. The most common types of grease traps are specified by the American Society of Mechanical Engineers (ASME) and require third-party testing and certification to ensure their effectiveness. These traps must remove a minimum of 90% of incoming FOGs:

  1. Passive Grease Traps: Passive grease traps are smaller, point-of-use units that are typically installed under sinks or adjacent to dishwashers. They are designed for lower flow applications and are more suitable for smaller kitchens or food service establishments. These traps rely on gravity to separate the grease from the water and require regular maintenance to prevent clogs.
  2. Large In-Ground Tanks: Large in-ground grease traps are used for high-flow applications such as restaurants or commercial kitchens with a significant volume of wastewater. These traps are installed below ground and can handle large quantities of grease and solid waste. However, they require more space and are more expensive to install and maintain.
  3. Hydromechanical Grease Interceptors (HGIs): Hydromechanical grease interceptors have gained popularity due to their compact size, high efficiency, and durability. HGIs are typically made of plastic or fiberglass and can hold a larger amount of grease compared to passive grease traps. These interceptors use a combination of mechanical and hydraulic forces to separate and remove the grease from the wastewater.
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Benefits Of Hydromechanical Grease Interceptors (HGIs)

Hydromechanical grease interceptors (HGIs) offer several advantages over traditional grease trap devices. These benefits have contributed to their popularity in commercial kitchens:

  • Space-Saving: HGIs are designed to be compact, making them ideal for kitchens with limited space. Their smaller footprint allows for easier installation and frees up valuable floor space.
  • Increased Grease Holding Capacity: HGIs have a larger capacity to collect and store grease, reducing the frequency of required maintenance and pumping.
  • Durability: HGIs are typically made of high-quality plastic or fiberglass materials, making them resistant to corrosion and other damage. This durability ensures a longer lifespan for the device.
  • Efficient Grease Removal: The design of HGIs incorporates both mechanical and hydraulic forces to effectively separate, trap, and remove grease from the wastewater. This ensures a higher level of grease removal efficiency compared to passive grease traps.

Maintenance And Cleaning Of Grease Traps

Proper maintenance and regular cleaning of grease traps are essential to ensure their continued functionality and efficiency. Neglecting the maintenance of grease traps can lead to plumbing issues, fines from regulatory authorities, and safety hazards in the kitchen.

Grease traps should be inspected frequently to monitor the accumulation of grease and solids. The frequency of cleaning and maintenance can vary depending on:

  • The size of the trap
  • The volume of wastewater
  • The specific regulations of the local municipality

During the cleaning process, the grease trap is pumped out to remove the accumulated grease and solids. This waste material should be disposed of in accordance with local regulations to prevent environmental contamination. Professional grease trap cleaning services are available to ensure proper maintenance and compliance with regulations.

Grease traps play a crucial role in preventing blockages in the plumbing system and protecting the environment from the release of untreated sewage. Different types of grease trap devices, including passive traps, large in-ground tanks, and hydromechanical grease interceptors (HGIs), offer various benefits and applications.


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Frequently Asked Questions

What is grease trap used for?

A grease trap is an essential plumbing facility designed to prevent the accumulation of fats, oils, and greases (FOG) in the municipal sewer system. Serving as a drain or waste pipe, it intercepts and separates FOG from wastewater generated in commercial kitchens. As these establishments regularly produce significant amounts of FOG, a grease trap acts as a barrier, allowing the FOG to cool, solidify, and be contained within the trap while allowing the rest of the wastewater to pass through. By capturing and containing FOG, grease traps help to prevent sewer blockages, protect the infrastructure, and ensure the smooth operation of the municipal sewer system.

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What are grease traps and how do they work?

Grease traps, also known as grease interceptors, are essential devices used to prevent the buildup of fats, oils, and greases (FOG) in drainage systems. Acting as a receptacle, they are specifically designed to capture FOG from wastewater before it enters the drainage system. The trap works by utilizing the principle of gravity and buoyancy. When the wastewater flows into the trap, the FOG, being lighter than water, floats to the top, while the heavier solids sink to the bottom. The clear water in between is then able to exit the trap and continue its journey through the drainage system. This separation process allows for effective FOG removal and prevents it from causing blockages and clogs in the plumbing system. Regular maintenance and cleaning of grease traps are necessary to ensure their optimal functioning.

What is the meaning of grease trap?

A grease trap is a crucial device in a kitchen’s plumbing system that prevents grease and oil from clogging the sewer waste system. As kitchen wastewater flows through the grease trap, it works to intercept and capture any grease present, effectively trapping it within the device. By doing so, the grease trap helps to minimize the negative impact of grease buildup on the sewer system, ensuring the smooth flow of wastewater and preventing potential blockages.

What is grease trap in wastewater management?

A grease trap in wastewater management is a device designed to separate grease, oils, and fats (FOGs) from wastewater before it enters the sewer system. It works by slowing down the flow of wastewater, allowing it to cool and causing the grease to rise to the surface. The grease then separates from the wastewater and is trapped within the grease interceptor, preventing it from clogging the sewer lines or causing pollution in the water treatment process. By effectively capturing FOGs, grease traps help maintain the efficiency and integrity of the wastewater management system.

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