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Fats, Oils, Grease (FOG) 

Fats, Oils and Grease (FOG)

Fats, oils and grease in the sanitary sewer system are a major source of problems.  FOG may appear harmless when it’s dissolved in a solution with hot water being sent down the drain, but as the liquid cools the FOG comes out of solution and begins to adhere to the inside of the pipe.  Some of the FOG will be left in the privately owned plumbing between the sink and the street, and some will make it out to the pipes under the street which are owned by the District.  Either way, the deposits left behind reduce the capacity of the pipes to carry sewage, and may eventually cause or contribute to a sewer blockage.

Field crews routinely clean and TV inspect the sewer mains located under the street, and are on ​the lookout for FOG problems.  When a sewer main is found to have excess FOG accumulations, the pipe is placed on an increased-maintenance schedule, so that it is cleaned more often to remove the deposits and keep the system functioning properly.  Unfortunately, the cleaning process itself may be somewhat harmful to the pipes due to the high pressures involved, and so too much cleaning may result in shortened pipe life.  In addition, some FOG tends to be corrosive (due to its low pH) to some pipe materials, and can also shorten the life of the pipe.  So the result of excess FOG in the sewer system is increased maintenance and shortened pipe life, which are costs shared by all of the District’s customers.

FOG Commercial Program

Sanitary sewer overflows (SSOs) and increased sewer line maintenance due to excessive FOG discharges have been on the rise.  This has prompted OLWS to step up its efforts to identify the sources of excess FOG being discharged into the sewer system.  The largest contributors to the FOG problem are food service establishments (FSEs), which include restaurants, delis, bakeries, meat departments, school kitchens, etc.  Some of these FSEs have grease interceptors which remove most of the FOG from the wastewater before it is discharged into the sanitary sewer.  A grease interceptor consists of a tank with a baffle system inside that slows the wastewater long enough for the FOG to separate and float up to the water surface, where it is trapped.  The gray water then flows out from under the trapped FOG layer and into the sewer.  Eventually, the FOG layer in the grease interceptor builds up and has to be removed – the tank is opened and the congealed grease is pumped out for proper disposal.

OLWS is working to TV inspect the sewer mains near all of the FSEs within our boundary to determine whether any FSEs have excessive FOG in their wastestreams.  If they do, steps must be taken to address the issue.  A change in kitchen procedures will sometimes correct the problem.  If not, the FSE may need to install a grease interceptor to trap the FOG until it can be properly disposed of.

OLWS encourages FSEs to have their grease interceptors maintained by pumpers who have registered with the Preferred Pumper Program.  These contractors have met certain criteria established by regional municipalities.  They use standardized procedures which increase the likelihood that grease interceptors are cleaned correctly in accordance with industry standards.  In addition, these pumpers assume responsibility for submitting completed pump out reports.

Additional Information:

  • In the process of being updated, refer to the former Oak Lodge Water Services' District Sanitary Sewer Code
  • Oak Lodge Water Services FOG Program, which includes the FOG Best Management Practices
  • Oregon Plumbing Specialty Code: Chapter 10 Traps and Interceptors
  • EPA Code of Federal Regulations: section 403.5 National pretreatment standards - Prohibited Discharges

Industrial Pretreatment Program (IPT)

The National Pretreatment Program is a cooperative effort of federal, state, and local regulatory environmental agencies established to protect water quality. The program is designed to reduce the level of potentially toxic pollutants discharged by industry and other non-domestic wastewater sources into municipal sewer systems, and thereby, reduce the amount of pollutants released into the environment from these sources. The U.S. Environmental Protection Agency has delegated DEQ the authority to approve pretreatment programs at the local level and oversee state-wide pretreatment activities. The communities approved to implement the pretreatment program have the legal authority to issue industrial user permits, conduct inspections of industrial and commercial sources, sample industrial discharges and enforce regulations. These programs also routinely perform self-monitoring to ensure the protection of worker safety, the sewage treatment plant operations, bio-solids and water quality.


EPA Pretreatment


Contact us at (503) 654-7765 or

Supporting Documents

2011OregonPlumbingSpecialty_Ch10.pdfOLWSD FOG Program 2017.pdf
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