Hi, I do not know your specific model Fun Finder. Both of ours used 3 inch ABS plastic pipe from the black tank to the drain valve. Fittings were all glued together except the valve itself which bolts together. The black tank drops out from below, so I doubt you need to pull the shower floor, even if you have to drop the tank. First thing is, are you sure the leak is at the coupling to the tank? If it is in the 3 inch ABS below the tank, you can cut a new piece to length, use 2 3 inch ABS couplers and replace it with tank in place. If it is the tank, I would pull the toilet, remove the bolts & valve plate and drop the black tank. Once out, flip it over and use fiberglass repair kit, being sure to rough up the surface well for good adhesion. Good luck.