Grease Interceptor
Most commercial food service establishments like restaurants, cafes and bars in Pierce County’s sewer service area are required to install a grease interceptor to control the amount of excessive fat, oils and grease entering our public sewer system.
Fats, Oils & Grease

Deep fryer

Fats, oils, and grease get into sewer pipes from dishwashers, garbage disposals, washing pots and pans and from being poured directly down the sink. This can cause big problems to the sewer system, such as clogs and backups. 

Even if you rinse your greasy dishes with hot water and detergent, it eventually cools and coats the inside of the pipes.
Report a Grease Interceptor Overflow:
(253) 798-7000

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What is a Grease Interceptor?

Diagram of grease interceptorA grease interceptor is a pretreatment device. Its main job is to filter your restaurant’s wastewater by capturing and separating fats, oils, and grease, and prevent the greasy sludge from blocking pipes. 

Without a properly functioning grease interceptor, you could end up with messy clogs and damages that can be costly to the County and the restaurant owner.

Where Can I Find My Grease Interceptor?
Grease interceptors are generally found outside of the building, close to the kitchen. It may be under a series of manhole lids or just one lid. 

If you have trouble locating your grease interceptor, please contact Pierce County at (253) 798-7202 or [email protected].
Why is a Grease Interceptor Important?

Grease interceptors are essential for:

Public Health
A properly functioning grease interceptor prevents sewage backups, protecting public health by reducing the risk of exposure to harmful bacteria and contaminants.

Environmental Protection
A properly functioning grease interceptor prevents sewage backups, protecting public health by reducing the risk of exposure to harmful bacteria and contaminants.

Maintaining Sewer Infrastructure
Preventing grease-related clogs is crucial for preserving the longevity of our sewer infrastructure. By doing so, we can significantly decrease the frequency of expensive repairs and minimize service interruptions.

In addition to blockages, excessive grease in the sewer system can turn acidic over time, accelerating the corrosion of concrete pipes and infrastructure. This corrosion, in turn, can result in leaks or even collapses. Regular maintenance and awareness about the proper disposal of grease are vital steps in protecting our sewer system's integrity and preventing costly issues.

A grease interceptor that isn’t maintained properly could result in:
Once reported, Pierce County may issue violation notices. Additionally, Pierce County staff conducts regular inspections throughout our Sewer Service Area and may take test discharge samples from your restaurant.

3-2-22 cleanout overflow to catch basinIMG_0568

2-25-22 GI overflow

How Do Grease Interceptors Work?
As fats, oils, and grease repel water and don't mix well together, grease interceptors mimic the same concept. Inside these interceptors, there are special chambers where the clumps of grease float on the surface of the water. This allows the cleaner water to flow through without carrying these greasy substances that could solidify and create blockages.

The frequency of maintaining a grease interceptor depends on usage. The rule of thumb is to have the chambers cleaned when the rated capacity reaches 25% of fats, oils, and grease. Once it exceeds this level, the amount of fats, oils, and grease entering the sewer system can start to increase.

You can also sample and test the discharge water in the clean out (often labeled "CO" on the lid) to make sure the fats, oils, and grease concentration is within the County’s local limits of 100mg/L. Fast food and busy restaurants are encouraged to maintain their grease interceptor about 2 to 4 times a year to prevent excessive fats, oils, and grease buildup and kitchen backups.

Cleaning Your Grease Interceptor 
During the cleaning process, make sure the grease is pumped out and removed from the walls and pipes of the grease interceptor. To ensure your grease interceptor is cleaned properly, work with a waste hauler who is knowledgeable of the local requirements for grease waste hauling and disposal. 

After cleaning, recharge the grease interceptor by pumping clean water back into the unit until water just starts running out of the grease interceptor discharge pipe. It may take some time to fill up with water to this depth, so allow ample time to complete this process properly. Once the clean water is filled to its appropriate depth, your grease interceptor is ready to return to service.
Graphic of Grease interceptor
Grease Interceptor Overflow
Grease waste overflows pose a serious threat to our environment and public health in addition to costly cleanup and/or fines.
Understanding Grease Interceptor Overflow
Grease interceptors can sometimes overflow due to various factors, including:
  • Improper maintenance: Neglecting regular cleaning and maintenance of grease interceptors can lead to blockages and overflows.
  • Excessive fats, oils, and grease discharge: Restaurants that discharge large amounts of fats, oils, and grease without proper pretreatment can overwhelm grease interceptors.
  • Mechanical failures: Grease interceptors can malfunction, leading to overflows if not promptly repaired.
What are Some Signs to Look for?
  • Slow draining water in the kitchen is a sign the pipes are clogging.
  • Grease and wastewater leaking out of manholes or backing up into the kitchen are also a sign of a serious blockage.
IMG_0575Reporting Grease Interceptor Overflow
If you encounter or suspect a grease interceptor overflow, please report it immediately to Pierce County Planning & Public Works at (253) 798-7000. You should also notify the contractor who maintains your grease interceptor system to address the issue. Quick reporting is essential to prevent environmental contamination and infrastructure damage.
Preventing Grease Interceptor Overflows
  • Regular maintenance: Business owners must adhere to routine maintenance schedules for their grease interceptors. This includes cleaning and inspecting them to ensure they operate effectively.
  • Proper disposal: Businesses should avoid pouring cooking oil, grease, and food scraps down drains and use designated collection containers instead.
  • Resources: Pierce County offers guidance to help restaurant owners manage fats, oils, and grease responsibly.
For more information or assistance, please contact us at [email protected].