: I have a shower that is only 2 years old. It is a standard liner, mud base, ceramic tile floor with a standard PVC type of drain connect to the 2" PVC drain line. A mildew smell comes from the drain all the time. When the drain is covered by something, the smell goes away. Drain line has been bleached, snaked, and checked to confirm that the P trap is holding its water seal. The builder is still under warranty and has broken out the entire floor to investigate. We found the mud base was wet across the entire floor and smelled bad when the tile was removed. Appears water was "spalshing" or otherwise getting into the darin weep holes and then wicking into the mud base. Plumber does not know what else to do. Has anyone experienced this problem with water getting into the weep holes? Clearly, our mud base once wet is not draining and drying either.
The correct drain to be used is called a "Tile shower pan drain" which sandwiches the pan membrane. Upon a water test of this we have found leakage will occue between the membrane and the subfloor unless additional adhesive is used to prevent this, and most likely only be severe during a backup.
For water to wick from inside a flowing drain through the weep holes and wet the mud bed to the point of a mildew smell is unlikely.
Sounds like water entered through a grout line and puddled under the mud bed, believe me, those grout lines in the corners can look more secure than they are.
Pan drain base needs to be on a level plain or just a slight bit lower then subfloor in order for weep holes to work, it's recommended that subfloor be graded toward drain (this can even be done with a fine sand) put some pea gravel around weep holes prior to mud bed application to ensure drainage.
Atleast the pan held the water and no other water damage was done, congrats to the plumber.
By all means, put new shower pan in and do a water test for 24hrs, check for leaks as often as you can during this period. Then drain and check for puddling.