The question- how to determine if there is a trap buried in the concrete? The situation- I am adding utility sink dwv to an area next to my whole home Water Softener. The DWV will tie into an existing 2 inch standpipe capped with a WS drain line at the top. There is an allowable air gap in the pipe itself for the WS line but I am puzzled by one thing. The WS line doesn't have the safety air hole incase there was a backup. I can add one no problem. But the curious thing is that the line was connected to the standpipe by a hole just big enough for the line to fit in. Now I don't smell any sewer gasses, but before I reconnect everything I want to figure out what the new vent situation should be once I connect the new sink Drain pipe. Should i add an AAV just incase?