Fats, Oils, Grease (FOG) Pretreatment Requirements

All food service establishments, including coffee shops, are required to pretreat their wastewater for fats, oils and grease (FOG). Pretreatment devices can be smaller grease traps located indoors, or larger grease interceptors located outside. These devices must be connected to collect all wastewater form 3-compartment sinks, floor sinks, floor drains, mop sinks, and prep sinks. 


A plumbing permit is required for installation of pretreatment devices in both new restaurants and remodeled establishments. This permitting process ensures an adequate system is being installed, you will pass inspection, and be able to open your doors.

Process for installing a pretreatment device: 

  1. Contact a certified plumber or licensed engineer to determine a correctly sized device for your facility
  2. Apply for a plumbing permit through the City of Kennewick’s Building Department – include calculations/map for the proposed device
  3. Once plumbing permit is obtained, install the pretreatment device and maintain it  

Frequently Asked Questions

What size device do I need?
Pretreatment device sizing needs to be determined by a certified plumber or licensed engineer according to The Uniform Plumbing Code. Sizing is based on fixture capacity or drainage fixture units in your facility.
Why are coffee shops required to install grease traps if they don’t serve food?
Coffee shops are included due to the fat in dairy products used to make the drinks and the oil in coffee beans. 

How often should I clean my device?
Grease traps and interceptors need to be cleaned regularly in order to function correctly. At any time, no more than 25% by volume of food or FOG should accumulate in the device. The City will work with businesses to help them determine a cleaning frequency that is adequate for their facility. 

How can I reduce my cleaning frequency?
Cleaning frequencies vary depending on the practices in each kitchen. The best way to manage FOG is to prevent it from going down the drain. Best management practices (BMPs) can be implemented to reduce grease trap/interceptor maintenance. Scrape pots and pans into the trash before washing, collect fryer oil in barrels to be collected for recycling, use strainers on sinks and floor sinks and empty the contents into the trash, train kitchen staff how to properly dispose of FOG and post BMP signs above sinks to remind employees.  

What is the best way to clean my grease trap/interceptor?
Larger grease interceptors are cleaned by permitted contractors who pump the contents of the device and dispose of it in accordance with local ordinances and environmental regulations. The City provides a list of vendors who service the area for grease removal. Smaller indoor units can also be emptied in this way or cleaned by the business owner/staff.  FOG should be skimmed off the top and all food removed from the bottom with a strainer and disposed of in a container resistant to leaking. Occasionally the entire contents of the device should be removed and mixed with a substance to solidify the contents and absorb water such as kitty litter, then disposed of in the trash. Next the interior can be wiped down to remove grease buildup on the walls of the device. 

Why are grease traps required?
When FOG is disposed of down the drain, it cools and hardens in sewer lines, affecting the infrastructure and leading to blockages. These blockages result in sewer overflows that propose health hazards, negatively impact the environment, and cause costly repairs. By pretreating the wastewater, contaminants are removed prior to discharge to a municipal wastewater treatment plant.