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# Thread: How much should the water level drop in a Kerdi Shower flood test?

1. ## How much should the water level drop in a Kerdi Shower flood test?

I have been researching Kerdi Flood testing procedures online and came across this thread over on John Bridge's tile forum.

The moderator there who answered the question is like Jim an engineer and one would think they have a solid understanding of building science. BBCAMP replied that the water level in a Kerdi flood test needs to be topped up after one hour. He goes on to state that if it leaks more than 1/8" you have a leak.

I worked out the math on a 1/8" drop oin water level for a 3'x4' shower and it equates to more than 4 bottles of wine in a 3'x4' shower.

This can't be correct? Can it? Of Course not.

Here is a shower of mine sitting pretty on hour 48. No loss of water and no drop in water level.

I use a tipped coin method of marking these Kerdi Shower flood test to make sure we read the exact water level.

I have never seen drops like this using Noble Seal TS, Kerdi, Hydro Ban or any of the liquids we use. What do you Kerdi men out there think? IS this common on a Kerdi Shower flood test? If so what are you doing wrong?

I emailed Schluter today and hopefully in a weeks time I can get an official reply back from them.

What do you think Jim? Would you say 1/16" level drop is OK? 3/16" drop? 3/32" drop?

I measure the water levels exactly when doing flood tests here in Vancouver and we measure for evaporation when needed?

Never have I had to "Top Up" a flood test.

You can see even Schluter showcases a flood test with their new installation video.

2. Hi,

The Schluter rep will typically say just the evaporation amount.

Pat

3. Pat how do you measure for evaporation?

Except during a flood test, a typical shower should never see much of any liquid water on the liner; and, if it is constructed properly, any that does get there will flow to the drain through the weep holes, if that kind of a drain is utilized and the liner is properly sloped (people that put the liner flat on the floor deserve any grief they get!). If it is something like a surface membrane shower, there may not be any weep holes, and, since it is then immediately beneath the tile which should be bonded well with thinset, there couldn't be much liquid water there at all since the thinset and tile are nearly a solid mass, bonded to the surface membrane.

Kerdi tends to bead water if you just drop some on the surface, so if you flooded it, it could take awhile for it all to become totally wetted, thus the initial drop in level. Then, any exposed thinset would absorb a little as well. Once equilibrium has been reached, except for evaporation, it should be stable. A drop after that reaching that initial equilibrium would indicate a leak.

Jim's buddy on John Bridge's site suggests that a kerdi flood test needs topping up. Do you have to do this as well?

Jim a second question for you. I thought that regular thin set and grout had a water absorbotion rate of roughly 17%. So the simple act of showering actually brings water into and under the tile. Grout is not waterproof.

Weep holes allow water that get under the tile and grout to migrate to the drain and down the pipe. Not sure your claim of flowing to the drain.

So your stating above that a Kerdi shower when flood tested can hold up about an 1/8" of water level then it drops and you top it up???

Lets argue that an average shower is 4'x3'. 1/8" drop is over 100 oz's or roughly 4 bottles of wine. If it was filled say 4" full off water it would have a cubic mass of 6,912 cubic inches or (6912 (cubic inches) = 29.9220779 US gallons) (6912 (cubic inches) = 113.267386 liters)

Since we know water weighs roughly 8.34 pounds an average Kerdi shower filled 4" in a 3'x4' shower is holding about 250 pounds of water and we are to believe that the Kerdi repells the water for an hour and then the water settles down. Kerdi is often sold as being "Magic" being "Hydrophobic"

Kerdi acts just like Jaeger membrane, Wedi membrane, Dal Seal and Noble Seal TS they all are waterproofing membranes and measuring the water level can be done in as little as ten minutes. Sooner if you poor the water in slower. Most water movement stops after 3-7 minutes of filling a shower for flood testing.

We use a tipped coin to measure the water level. Here is one from our last Kerdi Flood Test. The eater level did not drop 1/16" in 3 days. Never mind 1/8" in one hour.

JW

4. Weep holes and clamping drains are part and parcel to a conventional shower construction, and the gravity and draining on that was what was said. Except during a flood test, a shower NEVER should see pooled, liquid water on the membrane ever again (except possibly in a conventional shower's liner). The tile and grout will wick some, but because there's not a huge, thick, absorbant mudbed beneath, it dries to the surface quickly once you stop showering.

If you take some virgin Kerdi and sprinkle some water on it, it will bead up. Eventually, it will go into the fleece. Your picture does not appear to be of a shower, but some mock up and the Kerdi is not well adhered to the backing material. Initially, the water will bead up similar to a bead of water on a nicely waxed car, eventually, it will wet the surface and then the meniscus will invert. Water will wick a little into a seam, the more thinset you leave there, the further it will wick. If your seams overlap at least the minimum specified, it will not get beyond the seam into the backing material. That is the goal, and if done right will make a perfectly waterproof shower as once the tile is installed, very little water will ever get to the membrane and certainly not enough to pool long enough to do anything. That is the beauty of ANY surface membrane.

Once the fleece does get wetted, it also acts like the pad of a humdifier, and can significantly increase the amount of water lost to evaporation during any extended leak test. The small fibers significantly increase the surface area and lots more water will evaporate from that larger surface area. Just like in an evaporative cooler or a home humidifier.

Weep holes and clamping drains are part and parcel to a conventional shower construction, and the gravity and draining on that was what was said. Except during a flood test, a shower NEVER should see pooled, liquid water on the membrane ever again (except possibly in a conventional shower's liner). The tile and grout will wick some, but because there's not a huge, thick, absorbant mudbed beneath, it dries to the surface quickly once you stop showering.

If you take some virgin Kerdi and sprinkle some water on it, it will bead up. Eventually, it will go into the fleece. Your picture does not appear to be of a shower, but some mock up and the Kerdi is not well adhered to the backing material. Initially, the water will bead up similar to a bead of water on a nicely waxed car, eventually, it will wet the surface and then the meniscus will invert. Water will wick a little into a seam, the more thinset you leave there, the further it will wick. If your seams overlap at least the minimum specified, it will not get beyond the seam into the backing material. That is the goal, and if done right will make a perfectly waterproof shower as once the tile is installed, very little water will ever get to the membrane and certainly not enough to pool long enough to do anything. That is the beauty of ANY surface membrane.

Once the fleece does get wetted, it also acts like the pad of a humdifier, and can significantly increase the amount of water lost to evaporation during any extended leak test. The small fibers significantly increase the surface area and lots more water will evaporate from that larger surface area. Just like in an evaporative cooler or a home humidifier.

Jim this is not a shower but a test box.

This little box made to showcase a long term flood test. You can see how water climbs Kerdi and thin set. It tends to wick a good couple inches.

It's because of this that I prefer to reinforce these seams with Ardex 8+9 - more of a European installation system.

Look here in this European Kerdi Installation Video - There is no trace on Non-Modified thinsets in the seams....

6. All the chatter makes me want to avoid a membrane that isn't liquid... The more I read the more I don't like what I see.

7. The stuff works as a system, your Kerdi is not adhered to the surface properly, nor is that an approved corner, nor do you have the required overlap and there's too much thinset, where it is used, allowing the thinset to absorb moisture. If the stuff is anchored properly as if it was a real shower, you'd see different results - just like you would in a properly constructed shower. A proper seam has at least two inches of membrane overlap with a thin layer of thinset well embedded into the fleece. Mock it up as if it was a real shower pan, and you'd see different results...I know, as I've seen it. Days of being full of water and no evidence of moisture intrusion.

8. Jim that is mocked up like a proper shower.

Just like the Kerdi Handbook states I used drywall as a backer and the Kerdi trowel to apply the Kerdi.

I used a folded corner and banged in a screw. I was shocked that the water wicked so high as to hit the screw location and of course in a proper shower build we would not use a screw at all that close to the curb top.

What is wrong with my test box? I build showers every week and flood them sometimes for a week plus.

Not only do I test Kerdi I also test every other product we use. Never does a new system get installed by me and my crew before I run it through the paces at home. My wife does not love this testing so much since the Kitchen and Laundry Room are my chief lab areas!

Filling a liquid membrane box - Mapegum WPS

No wicking. This box took weeks and weeks to evaporate and the product did not blister or cause any failure to the cardbox file box lid I used as a pan to waterproof. We will be installing are first AKW shower pan soon and I wanted to run this new liquid membrane through it's paces.

This shower stayed under flood test for 4 days and the water level did not move a hair. If the advice that is given out by BBCAMP on John Bridge's site is correct does that mean a Kerdi shower is OK to drop by nearly a 1/2" in 4 days? I think not. I would flood test your Kerdi shower out for at least 3 days to be safe. If I saw any drop over say 1/16" I would be worried and most likely reset the test with an evaporation control.

JW

9. The Kerdi Cone Fold or Vortex Fold. Drip. Drip. Drip.

Jim how come this poster is not being help out by your buddies on John Bridge's site?

http://www.johnbridge.com/vbulletin/...ad.php?t=98196 Lazarus has posted in another thread he doesn't even preform flood test on his showers and his advise should be followed here??? Watch out people what you look up online. Lazarus is a screen name for Steve Pontious the owner of Avanti Tile and Stone or Avanti Tile and Marble. Seems Steve is unsure the proper name of his company on his Link'd In profile as of today anyway.

The discussion about Kerdi being Hydrophobic lead Steve to share with the group his love of Charmin Toilet Paper.

As posted and then deleted in the thread by the director of the NTCA. This mindless comments and banter is a proven thread removal approach and this approach is used often online. Often might be a strong word but used when needed. To gain insight into a problem you should ask yourself who's advice your listening to. Check out this thread on the Linkd'In NTCA group and see what you think. Steve tells a group of Tile men and women he uses or prefers Durock or Permabase but online only recommends drywall. He even claims to have done the test - but with no proof. Classic smoke and mirror show. Once again a John Bridge writer at the thick of the BS advice. No shocker there.

In countless posts Kerdi seems are claimed to not wick water past 1/2". 2" is spec'd as overkill. Why should you flood test? Look at the Kerdi Drain wicking water in the link I posted. Where is that water going? I would say into the mortar bed. The curb. The wall board. The drywall if your foolish...

10. Using too much, or too dry of a thinset layer underneath any sheet membrane, especially at the seams is probably the biggest error people make. Using the proper mixing, trowel, and the proper angle and this normally isn't an issue at all. A properly mixed thinset for this application can hold a notch, but just barely and a bit of slump may be better than nice crisp notches. If you embed the fleece properly, and you should pull back a section while doing this to check, then it will not wick past the mandated minimum 2" seam. The instructions say to wait at least 24-hours after installation of Kerdi prior to performing a flood test. Then, if you use a modified thinset, it may never perform properly. It all comes back to workmanship and following the instructions.

As I've said before, overnight, and especially over several days, in the winter particularly or if you happen to live in the dry southwest of the US, an 1/8" per day or more is not unheard of for the level to drop in a waterproof container, let alone one with fabric mesh on it that can wick a bit of moisture up into the air and significantly increase the surface area. My toilets will drop over an inch a week with the lid down while away on vacation...with the area totally open like in a shower stall...I'd not be surprised if it was more. Living in a temperate rain forrest is not the norm for most people...your results may differ. The RH in my place right now is 23%. Vancouver is likely much higher than that most seasons.

Then, you have to consider that except during a flood test, a shower will likely never again have standing water in it. Even a poorly installed one still takes a long time for the water to wick into an improper seam - far longer than a typical cbu would take to wick up from the liner far enough to cause damage there. From a test someone did, they found that cbu tends to wick up about 6" when sitting in liquid water which might happen in an improperly installed conventional shower with a waterlogged pan. This is likely cbu brand dependent, as some wick more than others.

11. ## Is Kerdi Hydrophobic? I say no. How can a material that wicks water be Hydrophobic

So yet another discussion on Hydrophobic shower membranes has been shut down. For those of you not members of the Linkd'In NTCA group I'll fill you in. I'm disgusted with these Hydrophobic claims nad have been asking anyone to prove it to me. By doing this I'm hoping more people will realize it is a stunt, a joke, bullshit, BS, a trick ...... etc. I even offered up a free linear drain!!!

Well one of the worst writers online joined the group and started with his nonsense and this lead to further debated. We learned that Steve likes Charmin toilet paper and the head of the NTCA shut the thread down. Bart (NTCA Director) tells me he received 50 complaints from 2500 members. Are you kidding me?

50 people are upset to a point to write the NTCA and say "John should not talk about Kerdi wicking water" or "I don't like this debate". I'm a little taken back and shocked that the discussion got closed. I'm even more upset that the comment;

This one

Was removed in the process. I feel it highlights the class of our man from Texas. Mr. Avanti Tile and Stone or Avanti Tile and Marble.

If you read the post above you will see Steve claims to prefer Durock or Permabase. If you follow his post of John Bridge's you wil see him recommending drywall? Why is this? And to openly claim to have done the Kerdi trick... That's funny. Steve claims to have done the "Magic Trick" and we are waiting for the video.

Now many of you regular posters may not like my rants but Terry's forum is one of the last "Clean" forums can find. Less edits. Less removals. Less thread locking and on and on.

I have a nice linear shower drain for anyone that can make a cone from Kerdi with a pin hole in the bottom and then fill it with water. If the Kerdi is "Magic" it will repel water from the seam and the pinhole. If the Kerdi is "Hydrophobic" you should have no issues. If the Kerdi wicks water like I have proven time and time again you will get a slow leak- drip, drip, drip, drip, drip.....

I have bitched about Kerdi for a long time online and in order to switch hats have gone to great lengths to find a setting where it can be used and satisfy my standards. I have come to learn that another German company Ardex allows the use of modified thinsets with Kerdi and not only do they recommend it they double the 5 year Kerdi warranty to Ten. Now you can still get lifetime warranties, 25 year and 15 year from some of the others waterproofing companies but for Kerdi this is twice the norm!

For more information on the ten year Kerdi warranty contact Robert Russell <Robert.Russell@ArdexAmericas.com> - Bob sent me the products from Ardex I need to qualify for this ten year warranty and send me the warranty in writting to my office!

As for that free linear drain (I only have one drain on the table for this offer). All you need to do is make a cone of Kerdi and poke it with a pin. Remove the pin and film the entire process. I would like to see the video posted on youtube. I'm not worried about loosing one of my linear drains since I have tried this same test over and over again with always the same result. Drip, Drip, Drip, Drip

JW

12. ## Failed Kerdi Board Hydro Ban Niche Detail.

So two months later and still the offer of a free Kerdi Line Drain on the table not one person can upload a video of the Kerdi Vortex fold. I love how many people claim to do it and that not one person will prove me wrong with video proof. It has been almost a year or more that I have tried to find anyone that can do it. No setter I have ever met can do this trick. Have you tried at home? Try it?

In my garage is a Kerdi Line drain. I'm going to keep the contest going another month and see if anyone can prove me wrong. If no one does I'll install this drain and show you the proper procedure (or at least my proper procedure) for making a water tight shower out of Kerdi.

I have mailed out now 8 of the Kerdi inside corners John Bridge and others have claimed to use. These corners sent to pros in the business.

I'm saving a few for my local BC rep - who told me he can do it but never send me a video. I'll bring them down to BuildEx next year and see if he can pull it off.

As for anyone else wanting a chance to win this drain from me - post those videos! Two minutes showing the Vortex Fold and the cup holding water.

I'm told the trick is to get a single drop in first to "Air Lock" the pin hole on the bottom. I can't do it. I've tried dozens and dozens of times.

In John Bridge's book he is preforming this trick over a sink and does not show the bottom of the cone.

Jim can I mail you a inside corner so you can try?

I have given Kerdi a really hard time online and mostly because so many people have no clue how to install it and even go as far as recommending their piss poor methods to the masses. What Kerdi does have going for it the most is - Technical Support. Top Shelf support and just recently got a glimpse of how good it really is.

I was approached to look at a failed Hydro Ban - Kerdi Board niche detail and asked how I would approach the repairs. In the resulting discussions I suggested that Dale Kempster be involved and he did come and help this user out. What I'm not impressed with is the workmanship in the first place.

I see poor thin-set coverage and glass tile over Kerdi Board.

I see wall studs exposed! That is brutal and this from a "Kerdi Certified Pro" in Texas.

I see missing framing and missing fasteners.

And I'm told the local Schluter rep inspected this job.

What you can't see is the back and forth from Dale and the client. I am totally impressed with the level of service Dale has offered up and that is worth something. I also am impressed with some of the finer points of Kerdi Fix and a little more convinced that technical support at a city level is no where near as good as technical support from head office.

This Schluter rep in Texas should have caught the finer detail notes Dale did and that I could see myself from just pictures.

Careful who you hire and if things don't look right - put the brakes on the job like this client did. They now have a repair plan in place and the assurance of the manufacture themselves.

Nice work Dale!

This is the niche detail. The problems started when the installer used a product from Laticrete that is not the equavalinet to Kerdi Fix as "Kerdi Fix"

The red in the picture is actually the wall stud - so there is no backer board there at all.

When questioned - I'm told the installer told this client "He is certified by Schluter" - Schluter replied that this is not right and gave this client options to do so. In the installers defence he did offer to build a better niche earlier to mine and Dale's involvement. That said - looking at the quality of this niche it appears that all steps are not being followed and perhaps our setter here in Texas needs another day or two at Schluter School.

JW

13. Originally Posted by JWhipple
So two months later and still the offer of a free Kerdi Line Drain on the table not one person can upload a video of the Kerdi Vortex fold. I love how many people claim to do it and that not one person will prove me wrong with video proof. It has been almost a year or more that I have tried to find anyone that can do it.
...because no one cares about it.

14. John, just did a kerdi shower in my own home. Used Kerdi board and kerdi styrofoam pan with membrane and kerdi drain. Of course after the board is all in, niches cut and sealed I read about the kerdi baord. Water tested a piece and it seems to be fin even when exposing the raw edge to water. Thank god it is a stud wall so hopefully the screws will hold it in. I used kerdi fix and applied it to all the seams that will or could leak on the kerdi for the flood test. I went with a very generous 3-8 inches of overlap so that I could be really sure of sealing. I am reading this post and just not sure If you like Kerdi or not. If the pan passes the flood test I am going to redguard the seams just for extra peace of mind and lay the tile. I am not researching into Wedi and it looks like a great product. I have built many bath surrounds with CB and even shower stalls using the vapor barrier method and never had a problem. I wanted to try a totaly waterproof shower so that is why I tried kerdi. Not sure how the outcome will be. Tha major question is : Do you like kerdi or not? And am I better off next time laying up CB and painting on liquid redguard and using a wedi preformed pan? or a Kerdi pan and drain and CB and redguard. Just looking for your ultimate bullet proof shower recipe and Opinion on whether I just made the biggest mistake of my life with Kerdi ?

15. Kerdi has been used for MANY years...if it regularly failed, you'd hear about it. As with anything you piece together, it all comes down to the workmanship. If you do it right (assuming it's a good product, and Kerdi is), it will last. Now, you could argue there may be better products. Just like there are lots of choices in life, what's best for one may not be the best for another. there are pros and cons to anything.

The only failures I've heard of with Kerdiboard are where they either were placed where there was excessive heat (uninsulated steam pipe) or the edge was not sealed at a joint properly, or the cutting technique delaminated it from the foam (as I understand it, that was a defective batch that was recalled and the process resolved - that was several years ago just after it was introduced).

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