How can I find where the water is coming from in my Leaking Tiled Shower?


I have an issue with excess water coming out weep holes. Fiberglass pan with glass wall tile on cement board. Looking for help in Annapolis MD.

I have a Sterling shower pan. Durock on walls. Cement patch on all seams. Redgaurd up 6" on wall from pan. Glass tile with mapei CQ grout.

After about a month of use a water spot showed up on left side outside shower stall at curb. Over the course of the past 10 days this is what we have done. Thru a hole there we can see corner of pan. We poked some holes in the back of wet wall and did a camera inspection. No sign of water. We checked glass door channels for any caulking issues. We decided to put some weep holes in the grout at the pan/tile intersection. When i poked thru, water seeped out.

I then decided to remove all grout at the pan. The CQ had turned to slurry. I cleaned it all out. Let it dry for 3 days. Then i caulked it with silicone and left 2 weep holes. After a few days use water appeared again.

Today we went back and let the shower run for 20 min. While running, we cut out a large panel behind wet wall and inspected all plumbing. No issues. No moisture showing on back of backer. After more than 20 min with water running, the water showed up thru the small hole. Turned it off. Wipes down walls and lip of pan. Water was still coming out weep holes after 10 minutes. A mapei rep came over this afternoon to consider the grout being the problem. He took a sample of the grout we removed 10 days ago to analyze.


ANSWER - First of all if it was installed correctly you wouldn’t have a problem.  To fully figure it out I would have to perform a forensic intrusive inspection, which probably isn’t practical for a small shower.

What comes to mind is:

  1. that you only ran the redgard waterproof membrane up only 6” over the Durock backer board.  Durock is a porous cementitious board.  Thus water that goes through the grout joints above the membrane will go into the board behind the membrane.

  1. The question is where is the water coming from that weeps out of the holes at the shower pan to tile transition?

    1. Shower pan receptacles are suppose to have a 1” high flange lip that the backer board overlaps.  Is there one?

    2. Is there a gap between the backer board and the horizontal flange as there should be?

    3. Doesn’t seem likely that the water migrates from above the 6” high membrane and drains over it and out.

    4. Seems more likely that the water is coming from the Durock or from behind the Durock onto the shower pan flange and then fills up and overflows to the outside.

  1. Typically leaks occur at transitions where there are gaps that can be susceptible to water intrusion.  All of the horizontal and vertical transitions (inside and outside corners) should be flashed with waterproofing and caulked with an ASTM C920 silicone sealant to make them water tight and to mitigate movement.

  1. If you had waterproofed the entire Durock then the only water that can be retained is what the thin-set can absorb, which would evaporate fairly fast.  Leaving the Durock exposed allows it to absorb water that can then migrate to the paths of least resistance which are the breaches within the waterproof protection.

  1. You said you verified you didn’t have a plumbing leak, but don’t rule it out unless it has been fully verified.

  1. All you can do at this point short of a full replacement, is you can remove all of the grout in the tile and fill them with an ASTM C920 sealant.  It is not a legitimate waterproof method, but it might be a practical solution to your situation.

Good Luck,

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