We are in the process of replacing our kitchen cabinets and sink in our condo unit, and came across the long PVC pipe that runs horizontally below the countertop and connect with the sink drain. In order to fit in the new sink, we need to lower this a few inches. I was a little apprehensive about touching this pipe, as I thought it might contain drainage from the unit above me. After looking around on this forum and others (I'm not a plumber by any means and I apologize if this is the incorrect forum), it looks like this may be the vent (about 40" from the sink) for the kitchen sink. Am I correct?