[trekkor]

Do you have access under the house to see if there is water damage?

Block the drain again and add water until it is about half way up the curb.
This is a flood test and will completely saturate the mortar bed.
Make a small reference mark on the wall to keep track of water height.
Let it set for 24 hours before you drain it.

Once the water sheds off the tile, you should clearly see water running out from all three weep holes below grade.

I suspect one or both of these things is happening:

1. the weep holes are blocked.
2. There is no pre-slope under the water proof membrane.
( should be 1/4 inch per foot to the drain from the farthest corner )

Either of these conditions will cause the mortar bed to become a haven from mold and bacteria, etc.

Report back after the flood test!

Also, how old is the installation? 25-30 years?


KT