I am remodeling my bathroom and replacing all the shower tiles. The shower was built in the early '80's and does not have a shower liner pan. It is just mortor in a concrete recess in the concrete slab. I am replacing all the sheetrock with mortarboard. My problem is the shower drain is an old type that does not have the multiple parts that enable you to place the liner pan membrane between with weep holes. Must I chip out all the concrete around the drain and cut off the PVC drain and replace the new drain that will accept the liner membrane?

I currently have all the tile removed and sheetrock. The floor still has a thick layer of mortar/concrete (not sure which). Is there an easier way to fix this problem?

Thanks

Randy