Kerdi Drain Sounds Hollow (Pics Included)

jaidogFebruary 8, 2012

I'm using the hybrid Schluter Kerdi Drain + Hydroban method in my shower. I had to glue the Kerdi Drain to the drain pipe prior to pouring the mud shower pan since I have no access from below. Mud shower pan was poured yesterday using Laticrete 3701.

Now that the pan has dried, I fear that I may have a problem. If I tap on the Kerdi drain, it feels solid all the way around except for a small section. The section shown between the screwdrivers has a definite hollow sound to it when I tap on it. I know there is mud underneath, but I also know the mud is not all the way upto the underside of the drain.

There is even a small hole that is visible in the second photo where it is obvious that mud is missing.

Do I need to worry about this?

If so, what can I do?

And, is the whitish discoloration on top of the mud normal?

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I'd use an epoxy syringe and inject a mix (loose enough to inject, but still as stiff as possible) of thinset into the hole at the edge of the flange.

Mix up the thinset to a loose, but not free flowing consistency. Let it slake. Mix again. Load the syringe. As soon as you load the syringe, inject it. Reload and repeat.

When you stick the end of the syringe in there, use a rag and your finger pressure to plug the sides.

As long as you can get decent fill to support the flange so there's no flexing of the flange you'll be in good shape.

Let the thinset cure overnight then do the tapping test the next day.

You can call Schluter Tech and see if they have any other ideas.

But my main concern is deflection. If you have no deflection, just the hollow sound, that's good. But I'd do the fill anyway.

If the flange can move, it needs repair. If the edge of the flange has lifted and it's above the level of mud, it definitely needs repair.

    Bookmark   February 9, 2012 at 11:13AM
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I spoke with Laticrete tech support and they suggested filling the hole with watery thinset. Doing it with an epoxy syringe as you suggest sounds like a perfect way to get the thinset as far into the hole as possible.

There is no deflection right now. I can press on the hollow portion of the flange and it does not move. But, I want to be safe and will use your syringe idea.

Thanks (once again)

    Bookmark   February 9, 2012 at 3:05PM
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Don't make it too "watery". "Watery" scares me. "Loose" is better. ; )

If too much water, when the water evaporates the cured solids will just turn to crunchy dust.

Your not the first one this has happened to, so no worries there. Nice job with the sloped mud! A nice way to spend a relaxing hour, eh? lol


    Bookmark   February 9, 2012 at 8:07PM
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The mud pan may take a pro like yourself one hour. It took me three and that was with a helper! But, really not that difficult.

Rather than take a chance with watery thinset, should I just squirt some epoxy into the hollow area under the flange? Or, should I stick with thinset?

    Bookmark   February 10, 2012 at 9:29AM
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