I've been demoing old lead and 40 mil pvc liners out of my customer's shower stalls and going back with the conventional new drain and 40 mil liner for the past 10 years. One of my tile suppliers wants me to look over a new sytem by Kerdi which has no pvc liner and no 3 part drain. It is a seven part drain with a ecb crack membrane like/ phelt "Kerdi" material and 1/2" thinset straight to tile slab leaving no need for a 1-4" portland/sand slab on liner under floor tile build up. Ask your supplier and write my back or better yet if you've installed one, spill your guts. much appreciated.