I got a hold of my guy. Installation of grease trap in condo unit Ok per code but frowned upon. City PI and Sewer prefer superbasin for building. Determination of what should be used and sizing is made by the Sewer Dept. not plumbing dept.
Grease trap can be removed and regular trap installed.
Condo is legal SF in IL, grease trap not required for SF. However grease trap required in multiple dwelling buildings exceeding 6 units. (Let the fight begin)

If it were my insp. I would be checking permit history on the property. It doesn't make sense to install 50 grease traps like that. They are way too expensive. I tend to be highly suspicious when dealing with condo conversions.

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Accurate Inspections & Consulting, Inc.
773/844-4AIC
Markus Keller