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February 20, 2024

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    Grease traps prevent fats, oils, and grease from clogging your home’s drains. They are typically required in commercial and industrial properties but not in residences. However, some municipalities may have specific regulations requiring grease traps on homes with a high volume of cooking or food preparation.

    Even if you’re not required to have one, there are good reasons to consider installing a grease trap in your home. This guide explains what a grease trap is, why and when you would need one for your home, and how they work. If you’re unsure whether your home requires a grease trap, check with your local government or plumbing professional.

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    What Is a Grease Trap?

    A grease trap, or grease interceptor, is a plumbing device that captures fats, cooking oils, and grease (FOG) and keeps them from entering your home’s drain and plumbing system. It allows wastewater to pass through while preventing food solids from entering the sewage system.

    Grease traps are often installed in food service establishments and commercial kitchens but may also be installed in residences. They can be either internal (inside your home) or external (outside your home) and come in various sizes and shapes.

    Diagram of a grease trap
    Image source: Adobe Stock
    Today’s Homeowner Tips

    Grease trap cleanings are easy. Ideally, your grease trap should be cleaned at least once every three months, but never let it get more than 25% full. You can use your grease interceptor to recycle gray water to use in your lawn or garden.

    Why Do You Need a Grease Trap for Your Home?

    Grease traps are important for two reasons: protecting your plumbing system from clogging up with FOG and reducing the amount of FOG entering wastewater treatment systems.

    Fats, oils, grease, and other food particles become solid once they cool down. As they harden, they can cause clogs, backups, and overflows. The buildup of FOG can also harm your home’s septic system. Installing a grease trap for your home can help protect your plumbing system from blockages.

    Grease traps can also help you limit water pollution by reducing the amount of grease that can enter wastewater treatment systems. Blockages in municipal sewer pipes can lead to raw sewage flowing directly into the groundwater.

    How Does a Grease Trap Work?

    A grease trap works by using gravity to separate FOG from wastewater. The FOG floats to the surface, the grease trap fills from the top down as grease enters it, and grease-free water exits into the sewer lines. This process removes FOG before entering your plumbing system or a wastewater treatment facility.

    In addition to gravity, some grease traps may also use baffles, a system of plastic wall structures, to help prevent FOG from entering your drains. Baffles are curved walls that help low down and better control the water flow rate as it enters the drainage system.

    This video demonstrates how a grease trap works to separate FOG from wastewater.

    7 Different Types of Grease Traps

    Below we’ve listed the most common types of grease traps. The most frequently seen residential ones are gravity grease traps and passive grease traps.

    • Gravity grease traps
    • Hydromechanical grease traps
    • Automatic grease traps
    • Passive grease traps
    • Grease recovery devices
    • In-ground grease traps
    • Above-ground grease traps

    Gravity Grease Traps

    Gravity grease traps are the most common type. These traps use gravity to separate the grease and oil from the water. The wastewater enters the trap, and the grease and oil rise to the top, while the water flows out the bottom.

    Hydromechanical Grease Traps

    Hydromechanical grease interceptors use a combination of water flow and mechanical separation for oil and grease removal from wastewater. These traps have a series of baffles and screens that trap the grease and oil, and the water flows out the bottom.

    Automatic Grease Traps

    Automatic grease traps use sensors to detect when the trap needs to be emptied. These traps are typically found in cafeterias and larger commercial kitchens and can handle more wastewater.

    Passive Grease Traps

    Passive grease traps are designed for smaller commercial kitchens and residential properties. These traps use a series of baffles and screens to trap the grease and oil while the water flows out the bottom.

    Grease Recovery Devices

    Grease recovery devices are used in conjunction with grease traps to recover the grease and oil for recycling. These devices are typically found in larger commercial kitchens and can help reduce waste and save money on disposal costs. That said, some homeowners interested in sustainability install them too.

    In-ground Grease Traps

    In-ground grease traps are installed underground and are typically used in larger commercial kitchens — rarely in homes. These traps are designed to handle a high volume of wastewater and can be customized to meet the kitchen’s specific needs.

    Above-ground Grease Traps

    Above-ground grease traps are typically used in smaller commercial kitchens and some residential properties. These traps are designed to be portable and can be moved as needed. They are also easier to clean and maintain than in-ground grease traps.

    How To Install a Grease Trap

    Installing a grease trap involves several steps. Most residential grease traps, including gravity, hydromechanical, automatic, and passive, follow these same installation steps:

    1. Plan your grease trap installation in a suitable location — usually under your kitchen sink or food preparation area.
    2. Locate the drain pipe under the sink and measure the distance from the bottom of the sink to the drain.
    3. Next, select a grease trap that fits within the space and matches the drain size and local regulations, if any.
    4. Attach the inlet and outlet pipes of the grease trap to the drain pipe using plumbing connectors and tighten them securely. Use plumber’s tape on the threaded connections.
    5. Connect the trap to the plumbing system, ensuring all wastewater flows through the trap.
    6. Test the system by running water through the sink and ensuring it flows through the grease trap before exiting through the rest of the drain pipe.

    It’s important to follow all local regulations and manufacturer instructions when installing a grease trap to ensure it is effective and compliant with any applicable law. If you’re not experienced with plumbing DIY projects or are unsure about local regulations, it’s best to hire a professional plumber to install your grease trap.

    Where To Get Help With Installing a Grease Trap

    If you’re looking to install a grease trap, there are a few options for getting help. First, you can search online for tutorials or videos that provide step-by-step instructions for DIY installing a grease trap. Or you can contact a licensed plumber or contractor who specializes in plumbing. They will have the expertise and experience necessary to install the grease trap properly and safely.

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    FAQs About Grease Traps for Homes

    Why would a house need a grease trap?

    If your home produces a lot of animal fats, oils, and grease (FOG), installing a grease trap helps protect your plumbing system and reduces your environmental impact.


    Where are grease traps usually installed in homes?

    Grease traps are usually installed in homes with a commercial-type kitchen or where a large amount of cooking is done. These traps are typically installed underneath the kitchen sink or in the basement and are designed to capture grease, oil, and other food waste before it enters the plumbing system.


    Are grease traps safe?Are grease traps safe?

    Grease traps are generally safe when properly installed and maintained. If you don’t routinely clean and maintain them, however, grease traps can become a breeding ground for bacteria and other harmful substances that pose health risks to you and your family.


    Editorial Contributors
    avatar for Jonathon Jachura

    Jonathon Jachura

    Contributor

    Jonathon Jachura is a two-time homeowner with hands-on experience with HVAC, gutters, plumbing, lawn care, pest control, and other aspects of owning a home. He is passionate about home maintenance and finding the best services. His main goal is to educate others with crisp, concise descriptions that any homeowner can use. Jon uses his strong technical background to create engaging, easy-to-read, and informative guides. He does most of his home and lawn projects himself but hires professional companies for the “big things.” He knows what goes into finding the best service providers and contractors. Jon studied mechanical engineering at Purdue University in Indiana and worked in the HVAC industry for 12 years. Between his various home improvement projects, he enjoys the outdoors, a good cup of coffee, and spending time with his family.

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    photo of Roxanne Downer

    Roxanne Downer

    Editor

    Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

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