The KERDI-DRAIN design allows connection to the shower's waterproof membrane. The membrane adheres to the drain's integrated bonding flange, creating a waterproof connection at the top of the drain assembly. The Durock and KERDI-DRAIN assemblies both feature fleece-covered bonding flanges. Oatey shower drains work with tile or marble showers that use a shower pan liner. The low profile design of Oatey drains make them easy to install in small spaces.
The WingTite shower drain, Durock drain assembly, Schulter KERDI-DRAIN and Oatey shower drains are among shower drain replacement kits on the market as of January 2016. The WingTite drain, which works with plastic or fiberglass shower bases, has an O-ring that seals it to the drainpipe and four latches that flip out under the shower base, clamping it into place. The Durock drain assembly works with the USG Durock shower system and also with traditional mud bed construction.
Oatey Shower Drains for Tile Shower Bases are designed for use with tile or marble showers where a shower pan liner is used. The low profile design allows for installation in tight spaces. Drain body solvent welds over 2" or inside 3" Schedule 40 DWV pipe. Reversible clamping collar is secured with 4 stainless steel bolts into brass inserts. 2" IPS threaded strainer barrel is adjustable to allow for easy height adjustment. Weep holes in the drain assembly allow drainage from the pan liner. Round drain barrel accommodates 4-1/4" Universal Snap-Tite Strainers available in a variety of designer finishes.
I believe the weight of a person standing in the shower causes the shower pan to flex, which opens a crack in the PVC drain base body or along the solvent weld between the drain base and the PVC drain pipe. If the crack is in the flange of the drain base (refer to the Oatey shower drain diagram in the above link), the leak could run horizontally along the subfloor and down the floor joist.