My son in law has an ongoing problem that has defeated 3 plumbers so far. Today he called me to have a look. It's a triangular shower cubicle with a base of plywood (we think) that has had the original tiled surface removed and replaced with new tiles. This was after the water ran down the wall of the room below. Then plumbers came and have obviously tried multiple bodges with bits of pipe, lots of sealant and a little round "plughole" with a lot of small holes as the "customer facing" drain. When daughter showers, the drain is slower than the incoming water, so this isn't very good.
Son-in-law had purchased a rather nice drain fitting off ebay, but found it was too deep for the space available, so the plan now is to cut it down, then bed it on sealant. The question is whether there is a "best" sealant for this. He will try to dry out the hole in the plywood first, and then try a ring of sealant into this messy hole, then build up a ring of sealant into which the metal drain surround will be bedded. The ring of the new metal drain surround is an almost exact fit in the hole in the tiled ply, so the sealant will have to seal any tiny gaps. I would imagine that there will be some chance of slight movement when the lady is standing in the shower, so the sealant needs to be very sticky initially then form a very firm but slightly flexible seal that can be stood on. Can one get very runny, grippy sealant to soak into the ply edges and then gradually build it up with progressively stiffer, more solid sealant that will bond to it?
When he got the old sealant bodge out, there were signs of water staining where the sealant should have sealed against the plywood edges of the raw drain hole.