Q: "What is a gravity grease interceptor and how does it work?"
A: A grease interceptor is a device connected to your plumbing system, which is specifically designed to remove Fats, Oil and Grease (FOG) from the wastewater before it can enter the sewer system. It works by slowing the flow of water to allow the FOG to float to the top where it is contained within the baffle system.

There are several types and sizes of gravity grease interceptors ranging from large 1000 to 1500 gallon in-ground units to smaller under-counter units, know as  hydromechanical grease interceptors.

Q: "How often should I pump out my gravity grease interceptor?"
A: The proper pumping and cleaning frequently is dependent upon many variables, such as type of food prepared, cooking and cleaning methods, volume of food or meals prepared and the size of your gravity grease interceptor. Lake County Special Districts recommends that all gravity grease interceptors be inspected frequently and owners use the “25% Rule” where interceptors are pumped out when the combined thickness of the floating FOG and settleable solids layers exceed 25% of the total liquid depth of the interceptor. All gravity grease interceptors should be pumped out at least once every three (3) months.

Q: "What size gravity grease interceptor should I have?"
A: To effectively remove FOG, a gravity grease interceptor must retain the water long enough for the FOG and settleable solids to separate within the baffle chamber. Lake County Special Districts suggests that gravity grease interceptors are sized to match the number of Drainage Fixture Units (DFUs) of the kitchen or source (see UPC Chapter 7) as follows:

Gravity Grease Interceptor Sizing
GGI Volume (gallons)
Example #1: Typical fast food kitchen = 17 DFUs = 750 gallon GGI
Example #2: Typical larger kitchen = 45 DFUs = 1250 gallon GGI

or for a smaller hydro mechanical unit, use the calculation sheet.

Q: "What kinds of problems do Fats, Oil and Grease cause?"
A: FOG in the sewer system builds up on the walls of the sewer lines, accumulates in pump station wet wells, creates odors and clogs pumping and sensing equipment. When FOG builds up on the walls of the sewer line it reduces the system's capacity and can result in complete blockage. This results in sewer backups and overflows, greatly increased man hours and maintenance costs, equipment downtime, and fines.

Q: "Isn't my business grandfathered in under the old rules?"
A: No, any food or restaurant establishment that does not have a properly sized and properly maintained gravity grease interceptor is in violation of the sewer use ordinance.

Q: "My business doesn't produce grease. Do I still have to install a large grease interceptor?"
A: Provisions were made in the ordinance to allow facilities with no or low levels of grease to be exempt from the requirements. The facility must provide information and sampling data which substantiates the request. Other facilities could request a variance from the sizing requirements and be allowed to install approved types of smaller interior hydromechanical grease interceptors and grease removal devices.

Q: "Will a garbage disposal affect a grease interceptor?"
A: Absolutely. The ground up solids that go through the disposal will settle to the bottom of the grease interceptor and take up valuable space. The reduced volume will lower the detention time of the device and will reduce its efficiency. The increase loading will also lead to an increase in needed maintenance frequency.

Q: "My restaurant doesn't have space to install an exterior in-ground grease interceptor. Are their other options?"
A: Special Districts Administration can permit the installation of certain types of interior hydromechanical grease interceptors and grease removal devices instead of exterior in instances of space limitations. However, smaller interior units require substantial increased maintenance and implementation of best management practices to maintain compliance and effective grease removal. Please contact Lake County Special Districts at (707) 263-0119 to be considered for interior hydromechanical grease interceptor approval.

Q: "How do I have a Gravity Grease Interceptor installed?"
A: Most plumbers and plumbing contractors install gravity grease interceptors and hydromechanical grease interceptors. All installations must comply with California Plumbing Code Requirements.

If you have any questions or would like additional information, please feel free to contact the Lake County Special Districts Administration at 263-0119.

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Lake County Special Districts
Telephone (707) 263-0119
Fax (707) 263-3836
230 N. Main St
Lakeport, CA 95453