Kerdi flood test failure - what now?

nc8861December 14, 2008

I filled up my 32x60 kerdi shower near the top of the curb and started the timer. Measured several times in the first hour. By 1 hour, the level had dropped about 1/16" to 1/8" of an inch, so I pulled the plug, to prevent any damage downstairs.

What now? How do I tell where the leak is? There was nothing obvious during the test . Some surface bubbles, but nothing steady. One of the corner pieces I discovered after pulling the plug did not appear to have a good seam at the wall floor joint, so that to me is priority #1 (I could smoosh it with my finger right at wall/floor junction and could see some water/air escape. But that's only my best guess. What to do? Do I let it dry and the try and see what still looks wet under the kerdi? Do I just put another layer of band around the edges?

So discouraged....

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Avanti Tile & Stone (Stonetech)

If you have a 2" overlap at every seam....and used an UNMODIFIED thinset for the installation, AND you properly bonded the thinset to the Kerdi flange, you should NOT have a problem. What was the surface you adhered the Kerdi to?

    Bookmark   December 14, 2008 at 7:46PM
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I used versabond which is slightly modified, but it's also used by every tom, dick, and harry over at the john bridge forums so I felt comfortable using it.

The bond to the flange appears ok - the thinset seems to wick some water up there at the drain, but I've seen pictures online of others that have had that happen as well, so I knew that that may happen.

The kerdi was applied over a mud bed.

I can always try another test and let it sit longer and make sure it's actually leaking and let it go down like 1/4" or 1/2", but b/c the kitchen is downstairs I did not want to take any chances.

Maybe I pulled the plug too early? Maybe the 1/8" of water (about 24 cubic inches or 1/10 of a gallon) just was the water that was wicking into the thinset and not going anywhere?

    Bookmark   December 14, 2008 at 8:05PM
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Let it sit atleast overnight. The amount of water that you'll lose and the rate at which you'll lose it (if at all) won't be enough to cause any real permanent damage.

    Bookmark   December 15, 2008 at 1:03PM
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But there was probably 20 gallons of water in the shower..?? This is an upstairs bath, with the kitchen below. I'm confused as to why you say it wouldn't cause any damage.

    Bookmark   December 15, 2008 at 1:30PM
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First off, You're not going to lose 20 gallons that quickly. Not unless there was a catastrophic failure of the Kerdi, and you would've seen that pretty easily the first time. You need to give it atleast enough time to be able to see where the leak is. That is, unless you want to tear it all apart and start fresh.

    Bookmark   December 15, 2008 at 5:35PM
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Thanks Bill. If it is leaking, then how do I tell? I asked this question several times over at johnbridge, but the answer I always got was: "it won't leak!".

Under the Kerdi I've got 2" of mud, then 3/4" plywood, then 1/2" plywood, then the ceiling void then drywall in the kitchen. So even if the water gets through slowly I'm unsure how to tell where it's leaking from.

A guy over there told me something else to try was to see if my test plug had a good seal. So right now I've got the kerdi drain filled up (but not over the flange seam) with the plug in. Just want to see if my plug/pipe seam is tight.

    Bookmark   December 15, 2008 at 7:26PM
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You should be able to see a darkening underneath where it leaks, especially being that you used a mud pan instead of the foam. That's what I'd be looking for.

    Bookmark   December 15, 2008 at 7:50PM
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In the main field there's nothing noticeable. If there's something on the edges or corners it would be obscured by the thinset. I was messier than most in my thinset squeezing/seams, etc.

Would there be any disadvantage at all of laying one more layer on the floor, with another band strip all the way around?

    Bookmark   December 15, 2008 at 8:06PM
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Avanti Tile & Stone (Stonetech)

I'd be inclined to think the small "leakage" you saw was, indeed a bit of water wicking into the thinset. With a 2" Kerdi overlap, maximum "creep" is about 3/8". A leak test puts more strain on a shower than normal usage does. Got any pictures? That would help.

    Bookmark   December 16, 2008 at 3:41AM
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Thanks lazarususa - I do have a few pictures. I will try and put them here in this post, but if it doesn't work I'll include the link to the john bridge forums where you can check out the few pictures.

The creep around the drain is way more than 3/8". Probably an inch or more. But at this point I've filled up around the drain prob. 2 or 3 times, and I haven't let it dry out there.

I may buy your logic about the thinset wicking soaking up the water b/c I was really quite messy with the thinset. There's a lot of thinset on the floor where the band and the membrane were joined.

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Here is a link that might be useful: My thread at john bridge

    Bookmark   December 16, 2008 at 8:47AM
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Here's another pic showing all teh thinset on the floor. See what you think.

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    Bookmark   December 16, 2008 at 8:51AM
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When you installed the trap and drain, it was cemented together, right?

What are you using to seal the drain? Meaning, is it effectively sealed?

The 1/8" water loss could be from a few things. When you pour water on Kerdi, the fleece can hold air bubbles on the fleece surface. As those air bubbles escape, and as the thinset absorbs some of the water, the water level will drop. A small effect.

Around the drain. If you think you have a bad seal between the kerdi and the flange, run a bead of Kerdi Fix right at the seam where the Kerdi meets the flange. Clean the surface, run a bead, and smear it so it lays flat. That'll seal it.

Now the corner piece that you said had a bubble behind it, and air/water leaked out? That's the only place I'd say really needs a closer look.

I'm not sure how "flappy" that corner piece is, but you can either seal it in place with more Kerdi Fix, or you can slice the bubble, inject a little thinset behind it, set it flat, let the thinset cure, then cover the repaired area with another piece of Kerdi with 2" overlap extending past the sliced area and on to the "good" kerdi.

Give those repairs time to cure, then try another water test.

You can partially fill the pan to make sure you're not leaking at the drain of the drain flange. If successful, then you can do a full-depth water test.

Let the water test run longer, too. You may get that 1/8" drop, then no more drop. That usually signifies the drop was due to entrained air coming out or water being absorbed by the exposed thinset.


    Bookmark   December 16, 2008 at 10:47AM
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Thanks Mongo! Here's some answers...

Yes, I did cement the trap and drain. It was ABS (black) and ABS cement (man that stuff sets fast!)

I was using an Oatey 2" test plug - the kind that has a wingnut that tightens and expands a rubber seal to meet the piping.

I will bite the bullet and buy some kerdi fix.

    Bookmark   December 16, 2008 at 11:25AM
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Make sure you flood these showers for 72 hours. A slow leak will not cause a ton of harm to your home if your happy with more mould, more bugs and more rot.

72 hours - Yes
48 hours - so/so
24 hours - the least you can do by code. THE LEAST PEOPLE!!!

Make sure your crew flood test these showers every time - every job...

Does any one know where I can find some pictures of "Passed Flood test and Kerdi" ?

I can't find any online....

I did see another online poster applying Hydro Ban to a Kerdi Board / Kerdi shower - I wonder why he did that???

I know why? The same reason I do it. I bet you are pressed to find a flood test picture with out it....

Would love to be proved wrong here - does anyone have a picture of a plain Kerdi Shower Pan under a 72 hour flood???

Please share!

    Bookmark   September 4, 2010 at 8:49AM
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