I'm preparing to replace a shower pan and then install tile in my shower stall. The installation will be in a depressed pit in a concrete slab. I'll probably use a molded, one piece pan. Question: How can I test the connection to the PVC drain pipe, coming from the pit, prior to installing the pan and after installing the pan before I tile the walls? I'm doing this project because there was a leak at the old connection. Lots of water, damaged floors and mold.