We are setting a flange in our shower pan. We will float the pan with mortar.
The drain is being moved in order to accommodate proper slope. It would have been too steep in the current location.
The plumber is not willing to move the pipe before we set our flange. He wants us to set it in the pan and the next time he comes this way he will attach the drain pipe. But if he pushes too hard while setting the pipe into the flange, there is the possibility of damaging the waterproofing around the flange.
My thoughts are to put it in writing what we will do: set the flange in the pan and tile before drain pipe is attached and that if there is damage to the tile or waterproofing, it would be the plumber that pays for the repairs needed.
Should we do that or insist that the drain pipe go in before we set the flange?
I have run into this issue a lot in the past. First, I would talk to the plumber and also let the general contractor know what is going on and explain the liability involved. They both need to understand that you are using a topical waterproofing that could be damaged if pushed on from below.
If that does not get you anywhere and they still are not willing to move the drain for you, then yes. I would get it in writing.
When you follow the manufacturer’s instructions for installation you’ll be surprised at how strong the bond is. You want to make sure the mud is coming up through the holes on the outer rim of the bonding flange. This will help lock it in place. When I have had to do this in the past, as an insurance policy I would use a countersink bit (see picture right) and make the pre-drilled holes in the bonding flange the right size to accept a decking screw or a stainless screw. Install these four screws prior to mudding your pan. As long as you drill the right size hole, the screw head will be flush with the bonding flange, will not interrupt your waterproofing and will help ensure the flange stays in place while reconnecting the 2″ pipe from below.