Every grease trap fills up. Grease floats, food solids sink, and the working space in between shrinks with every service. Once the trap passes a certain fullness, it stops separating grease and starts sending it downstream. Regular pumping resets the trap before that point. If your pumping is due, overdue or you are not sure when it was last done, call to talk to a provider serving your area.
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What a pump-out removes
A grease trap separates kitchen wastewater into three layers. Fats, oils and grease float to the top. Food solids settle to the bottom. Relatively clear water sits in the middle and flows out to the sewer.
During a pump-out, the provider removes all three layers, not just the top. A complete pump-out leaves the trap empty so it can be checked and refilled with clean water before the kitchen starts using it again.
- The floating fats, oils and grease layer
- Settled food solids and sludge
- The wastewater layer between them
The 25 percent rule and how frequency is set
Many local authorities use what is often called the 25 percent rule: a trap should be pumped before the combined depth of floating grease and settled solids reaches 25 percent of its total liquid depth. Past that point, separation drops off and grease begins to escape.
Pumping frequency is set around that limit. A provider may measure the layers on the first visit and recommend an interval that keeps you under it. Some authorities also set a maximum time between pumpings regardless of fullness. Where both apply, whichever comes first usually governs.
Menu, meal count and kitchen habits all affect how fast the trap reaches that point. A fryer-heavy kitchen can hit 25 percent in a couple of weeks, while a light-prep kitchen may take far longer.
What the provider should leave you
Pumping is only half the job for compliance. Inspectors usually want proof that the trap was serviced on schedule and that the waste went somewhere appropriate. Before the provider leaves, ask for:
- A service record with the date, trap size, volume removed and condition
- A disposal manifest showing where the waste was taken
- Notes on damaged parts such as baffles, lids or gaskets
- A recommended date for the next pumping
Keep these together in a binder or digital folder near the kitchen office so you can produce them quickly when an inspector asks.
Signs you are overdue
- Slow drains or standing water in sinks connected to the trap
- Strong odors around the trap or floor drains
- Grease visible at the outlet or downstream cleanouts
- Backups during peak service
- An inspector noting excessive grease or a missed interval
If drains are backing up now, stop running water to the kitchen drains until the trap is pumped.
What happens to the waste after pumping
Grease trap waste is not ordinary trash. Providers typically haul it to a permitted receiving facility, such as a treatment plant that accepts trap waste, a rendering operation or a facility that processes it into biofuel or digester feedstock.
The disposal manifest is your record that the waste reached one of these destinations. Improper dumping can create liability for the business that generated the waste, which is one more reason to keep every manifest on file.
Planning ranges for pumping costs
Pumping costs depend mainly on trap volume, how full it is, access and disposal fees. As a general planning range, indoor trap pumpings often fall between $115 and $475 per visit. This is not a quote. Pricing is set by the provider before any work starts.
Grease trap pumping questions
How do I know when my trap was last pumped?
Check your service records or manifests from the last visit. If none are on file, tell the provider when you call; they can measure the layers and help set a starting interval.
Does pumping include cleaning the walls and baffles?
Not always. Some providers include scraping with every pump-out, others offer it as a separate cleaning. Ask what is included before the work is scheduled.
Can I set up a recurring pumping schedule?
Yes. Many providers offer regular scheduled service, which makes it easier to stay under fullness limits and keeps your records consistent.
Do I need to be on site during the pump-out?
Someone should be available to give access to the trap, confirm the work and receive the service record and manifest. Ask the provider what they need from you.