Attempting to locate the bathroom rough-in located in the finished basement with floor tiles. The previous owner tells me there's a dap out located in the floor for the toilet. How can I locate this dap out without pulling up the wrong tiles? I tried using a magnet sliding it across the floor in hopes to feel the magnetic force. Thus far unsuccessful. Thanks!

A magnet won't pick up on PVC or ABS drainage. The tub dap-out will be located about 15 inches off one wall and right next to another. Simply take and tap around the most likely spots. When you here a hollow sound then bust up the tile. The toilet stub-up can be found 12" off the finished wall. If you've located the tub the toilet should be right near it. Or, you could call in a locating service such as Blood Hound. Blood Hound Underground
Good luck, Tom