Grease Interceptor
CSI Division 22, Plumbing
A plumbing device installed in a commercial kitchen's wastewater line that separates and traps fats, oils, and grease before the wastewater reaches the municipal sewer system, sized based on the kitchen's actual fixture flow rates rather than a single standard size, and required by most local codes for any food-service establishment.
Why it matters
An undersized grease interceptor can't handle a kitchen's actual peak flow, letting grease pass through into the municipal sewer system where it accumulates and causes blockages, which is exactly the problem the code requirement exists to prevent, making correct sizing a real compliance issue, not just a design preference.
On a real project
A restaurant's plumbing engineer sizes its grease interceptor based on the total fixture flow rate of every connected kitchen fixture, sink, dishwasher, floor drain, rather than a generic size assumed to work for any restaurant.
Who this matters most to
A Plumber installs the grease interceptor and connects the kitchen's fixtures to it. A MEP Engineer calculates the required sizing based on the kitchen equipment's actual flow demand.
Where this goes wrong
A restaurant's plumbing contractor installs a standard-sized grease interceptor without calculating the specific kitchen's actual fixture flow rate, assuming one size fits most restaurants. The undersized interceptor lets grease pass through and cause a sewer blockage within the first year, and the local utility requires the restaurant to install a properly sized replacement.
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