I recently purchased a condo in the City of Chicago, where the inspectors are notoriously, let's say... uncompromising.

Each unit in the building has a grease trap under the kitchen sink. Seems like overkill, right? However, the building was an old 1920s bank building and apparently did not have a building, grease trap.

There is no disposal under the sink and I want to install one, but do I need to remove the grease trap altogether? Can I leave it there and run the output of the disposal through the grease trap and periodically, clean it out?

Are you on a sewer or are you on city sewer? Back to you, Tom

This would be city Tom, my city.

Why not just ask inspector is grease trap is required? If grease trap is not longer required just remove and plumb disposal directly to sewer line?

Christmas time in Chicago it is the custom to ask your inspector a question written on a $100 bill

Back to my original question. Are you on a septic system or are you on city sewer? A separate drain line and grease trap are required on septic systems. If the building is on a septic system then a grease trap is necessary. Do you have a washer set up in your unit? Back to you, Tom

A quick phone call may help you to avoid that $100.00 "gratuity", Bob! Otherwise, in my area, there are NO garbage disposals allowed to enter a grease trap... the solids add to the gunk and will definitely increase the frequency of cleanings needed over time. I don't know how often, if ever, you have cleaned the existing grease trap, but it is a nasty job that is not something I would recommend to anyone (unless someone is paying me $125.00 per hour, of course).

Mark