We recently bought a house built in 1968. Before closing, we’d noticed water damage over the downstairs entry from the master bedroom shower, upstairs. When I removed the drain cover, I found the end of the PVC drain pipe…and that’s all. No flange or anything to keep water from going around the drain pipe, into the floor. Is there a coupling or flange I could install without ripping up the floor or shower stall? There is very little room for additional connections in the floor/ceiling space under the shower stall.