If I correctly recall your saga, you had a supposedly well built mud bed with supposedly well installed marble tile over it. Then you brought in a friend to seal it. After sealing is when you had the issues. If I recall, when the drain was later pulled, there was evidence that the sealer had percolated down into the mud bed. In a properly working shower, tiling over existing tile can be done. My understanding is your shower is broken. My understanding is that what forensic work has been done to your shower has not resulted in a cause of failure. It has only resulted in people pointing fingers at the other guy. The sealer guy points at the tiler. The tile guy points at the sealer guy. The GC shrugs his shoulder and points at you because you brought in the sealer guy on your own. You point at the GC and ask when will my shower be fixed? If no one can define the problem, how can they come up with a solution? They can't, so they all wink at each other and say "let's cover it up!" The only way to properly install new tile over bad tile that is on a bad mud bed is to completely isolate the new work from the old. There are three important points of contact: That means a NEW membrane has to be installed on top of your old work to prevent water from percolating down into the old work. That means that around the floor perimeter, the new membrane has to be tied into the wall's drainage plane or the wall's membrane that was installed behind the current wall tile. That means that the new drain has to be properly detailed into the old. So, what can you do? You can simply do what has been recommended. Simply cover over what you have. Bury it. Fingers crossed. Hope for the best. It's the easiest. You might have no further bad symptoms. Or the pan might start showing problems, 6, 12, or 24 months down the road. Or you can cover it up keeping the three points of contact in mind. Do understand that this route would require a conscientious and competent mechanic. Or go with the choice that over the long run will likely involve the least amount of labor, be the least expensive solution, and have the greatest chance of success: Have a competent mechanic remove the failed bed and install new. I wrote too much. (sigh) Good luck!

The photo I posted above is a bonding flange drain that was shown in one of Mr. Starykov’s articles on this subject. When I saw the orange membrane, I assumed it was a Kerdi drain. My post should just refer to bonding flange drains in general. Sorry for the confusion. I am a newbie re: shower pan construction. I‘ve just been doing a lot of research recently in order to avoid having my marble discolor due to water retention. I have read several discussion threads where specifically Kerdi drains + issue with water pooling around the drain have been discussed. These included comments by well respected professionals who would be able to identify a Kerdi drain. There is always is the possibility (probability??) that the dams around the Kerdi drains were caused by installation error. Anyone who spends even a little bit of time on Houzz looking at bathroom renovations knows all too well how often these shower pans are not built correctly! I think catbuilder has “nailed it“ in the above post - there may be (i) too much thinset used to set the drain, (ii) a dam that’s been created around the drain (drain wasn’t firmly set into the the thinset?), or (iii) a valley in the deck mud around the drain. Catbuilder clearly has quite a bit of knowledge re: shower construction/proper waterproofing methods. I do have a question for you - is the marble tile that you’re having an issue with the same as the marble installed previously without issues? There have been a lot of discussions about how the particular quality of the marble tile being installed may have some bearing on the rise in marble discoloration issues. There is a lot of marble being sold in the marketplace that is labeled as ”Carrara” but is actually not from Italy. My understanding is that the density/porosity of marble can vary quite a bit between different varieties. It also can vary somewhat in the same variety. If I hold up two of the Italian Carrara tiles I’ve recently purchased for my shower walls to a light source, certain tiles are much more translucent than others even though they were sourced from the same area. This would contribute to the amount of water being retained inside the actual stone. Then again, if you have a dam or birdbath around your drain, your marble tile is going to soak up some water regardless of type! I REALLY want a marble hexagon shower floor - but all of this is making me VERY ANXIOUS. I specifically decided not to purchase the standard Carrara hexagon mosaic tile that I really wanted since white marble tends to have more issues with this - but if my shower pan has any type of water retention issues, I still will wind up with discolored tile.

Can you take off that tile and take a picture of the curb? did he do a mud bed? a mud curb? cement board? Kerdi? this is mine. mud walls and mud curb. also notice my hex floor tile was put in first, so the wall tile could come down on top of it. looks much neater that way BTW, if he was a real pro, he would have laid those mosaic floor tiles first, and then done the wall tiles. All of those edges are going to have to be cut to fit against that bottom row of tiles. you know how difficult it is to get a good cut on those small tiles? And I bet he's going to use grout. It's a no-no. Don't even say anything. ask him how he's going to fill the joints between floor/wall tile and those vertical corners. bet you dollars to donuts he grouts everything. How was the niche built? preformed niche or cement board? if the latter, was it prepped like this all that tape will then get a coating of thinset, ditto all the seams and holes. The curb should have no screws at all. For you to say "it's underway and can't do anything" is ridiculous. You're paying for the job, yes? Do you know how easy it is to go out and buy a quartz backsplash and cut it for that curb? or for the tile guy to go to a stone yard and find a remnant quartz or stone castoff?

We didn't take pictures, but we know the drain system and the pan is perfect because it wasn't the first test we did (out of three tests). In the first test, the drain wasn't tightened down enough and all 8 gallons of water funneled from 2 points in that flange into our dining room ceiling. We cut out all the sheetrock and left the ceiling open until we got the drain clamped tight and the water, filling all 4 corners to the top of the curb, held without a hint of leak for 72 hours, then we repeated the test again to be sure. (Only then did we repair the ceiling.) We used a foam bulb shaped drain plug made and provided by Hydroblok just for the purpose of the flood test. We followed Hydroblok's directions: "The supplied screw hook can be screwed into the Foam Test Ball to act as a handle for inserting and removing the ball from the drain opening. DO NOT insert the supplied Foam Test Ball more than half way into the drain pipe without using the supplied screw hook or it may be difficult to remove."