I can't figure out how to take out my shower base, by that I can't figure out an easy method to disconnect the drain pipe from the base unit. The drainpipe is surrounded by a rubber gasket about 1/2" thick that comes to just below the flange. I can't turn the flange that seats into the shower base (silver) and there's no way to grip it. Is this rubber that surrounds the 2" black pvc just slipped around the pipe to create the seal? Is this what they refer to as a caulk seal? This shower unit was installed in the new house in 1980. I don't want to cut the base in half to get it out but I know of no other way. Somebody please help me.