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Difference Between Grease Traps and Grease Interceptors

    Grease and water don’t mix, especially when they travel through the sewer lines. It is for this reason that grease traps are essential in commercial kitchens.

    Food service industry wastewater filled with grease, oils and fats flows from the kitchen sinks and travels through pipes to enter the treatment plant. That’s why regular restaurant grease trap cleaning is mandatory.

    However, treatment plants are not equipped to handle grease. Plus, when grease solidifies, it blocks water pipes, causing sewer backups, also known as sanitary sewer overflows. Local and state ordinances require the use of grease traps and grease interceptors to prevent sewage backups.

    Restaurants are not the only structures to benefit from grease traps and grease interceptors. Hospitals, malls, schools and other establishments require the installation of grease traps to avoid clogging the sewage lines and being fined as a result of any blockages. Fixing the internal plumbing systems of the establishment where a sewage blockage occurs leaves the business with unprofitable downtime for the duration.

    Not only is the installation of grease traps or grease interceptors required in many establishments, but regular maintenance is also a necessity. Traditional grease traps must be cleaned out after 25 percent of their volume is filled with grease. Not engaging in frequent cleanings ensures that grease and oils accumulate in the sewage system, leading to messy sewage backups.

    Whether an establishment has a large-scale kitchen or a smaller one, a grease trap or grease interceptor is required. While both a grease trap and grease interceptor help prevent sewer line clogs, there are distinct differences between the two.

    Regularity of Cleanings

    Due to the small size of grease traps, these mini traps require cleaning more often. Since grease traps are generally small, the grease builds up faster inside them. Ideally, grease traps should be cleaned monthly by specialists or daily by employees.

    Grease interceptors are larger. As a result, grease interceptors can hold more grease and require cleaning less often. Typically, grease interceptors should be cleaned once every three months.

    Businesses that have a grease trap or grease interceptor on the premises should be aware of the ¼ rule. The ¼ rule provides a good estimate on when to clean on out the grease trap or grease interceptor. When the trap has filled to ¼ of its size, the grease should be pumped out. This rule applies no matter if a month or three months have passed.

    Flow Rate

    Low volume flows require a grease trap. The grease traps work well with the low water pressure (less than 50 gallons per minute).

    Kitchens with a high volume of flow, such as more than 50 gallons per minute, will have a grease interceptor. Large-scale establishments install grease interceptors, as they are fully equipped to handle the extensive grease flows through the drains.


    Grease traps, being relatively smaller than grease interceptors, are installed beneath the kitchen sink.

    Grease interceptors, however, with their large size, are installed outside of the building or underground. Local ordinances may have a say in where a grease interceptor should be located. Grease interceptors work well if the devices are located close to the fixture they serve. Ideal locations could be an adjacent room or under the fixture served.

    Foul odors emanate from grease interceptors, so they should be placed away from the areas where restaurant customers frequent.


    Grease traps are usually the size of a bread box. Sizing can vary, usually between 10 gallons and 500 gallons.

    Grease interceptors, with their larger holding capacity, are typically the size of a mini fridge. Grease interceptors feature a holding capacity of 500 gallons on up.

    An establishment can figure out the ideal size for a grease trap or grease interceptor by considering whether it is a facility with low, medium or high grease production. For instance, a convenience store, delicatessen, snack bar or sandwich shop will produce low grease flows. A coffee house, pizzeria and ice cream parlor typically produce medium grease flows. High grease flows are produced by cafeterias, bakeries and family restaurants.

    Grease Pumping

    While grease traps may be cleaned by hand, grease interceptors require the service of specialists. Technicians operate a large hose that pumps the grease from the interceptor to a truck equipped with a tank that holds fluids.


    Grease traps feature materials, such as steel, plastic, fiberglass and PVC. Rusted grease traps cannot be repaired and must be replaced. Cracked grease traps, too, cannot be repaired and should be replaced.

    Grease interceptors are made from cement, PVC or fiberglass materials that can withstand the elements while being situated outside.

    The fats, oils and grease (FOG) that accumulate in food wastewater are hazardous to sewer lines. In fact, grease traps were invented in the 1880s and its technology has remained nearly unchanged ever since. Whether the unit is a grease trap or grease interceptor, the technology works the same. FOGs float to the surface, leaving the wastewater to flow into the sewage system.

    When your restaurant or food establishment requires the services of Chicagoland’s most reputable cooking oil experts, turn to Mahoney Environmental. With over 60 years of dedicated service to Chicago and it surrounding areas, Mahoney Environmental offers an extensive list of services that are advantageous to the food service industry.

    Satisfied customers have benefited from Mahoney Environmental’s cooking oil equipment installation services, fresh oil delivery and waste cooking oil collection and recycling. Focused on sustaining a clean and green cooking environment, our team at Mahoney Environmental provides exceptional service and industry standard automated equipment.

    To learn more about our commercial kitchen grease trap cleaning and maintenance services call us now at (800) 892-9392.

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