Difficult Kerdi drain connection vs. cast iron clamping drain

[alember]

Hi all, thanks for the good humor and candor found here to say nothing of the outstanding advice.

Though I have read and read read till the cows come home and done numerous searches, I can't seem to find an answer to my question. So I figured I would just ask it.

I have, in the middle of construction, a 3' x 4' steam shower area with a cast iron clamping style drain resting on a 3/4" plywood subfloor. I would like to use kerdi on the ceiling and walls because of it's vapor and waterproof qualities and seeming ease of use. I do realize that the Kerdi drain would be the best drain to use for the obvious reason that it is part of the Kerdi system and would keep the mortar bed dry. My problem is this:

I cannot access the connection between the drain and the cast iron U-trap once the plywood is back together (I would remove some of the plywood in order to remove the current cast iron drain, install a PVC to Cast Iron adaptor and then the Kerdi drain). In the Schluter video, it would seem that you must "settle" the drain into the mortar bed (and presumably connect to the trap from below, afterwards). In my case, the drain will be fixed and immovable prior to my setting the mortar bed unless I glue the drain to the adaptor at the same time that I set the drain into the mortar bed. But that would leave me precious little time to make sure that the drain was level as PVC cement sets so quickly and I have never really done any of this before. What do the pro's do in this situation?

Alternatively, I could leave my cast iron drain in but nowhere in these forums could I find a clear discussion on how to marry Kerdi and a clamping drain style shower pan (even if the Kerdi is only on the walls and ceiling).

Thanks for any input,

al

[MHI]

Hi Al,

I would be best to get rid of the cast iron if you want to use the kerdi drain. There is no way to combine parts of both. It would also be best to make the connection as you set it in the loose motar. Try to make the drain pipe plumb, you can put a level on top of the square cut end to do this. This way there will be a good chance the drain will be level when you push it down. Pack the loose motar around the drain opening first, then glue the parts, push it down and hold it until its sets (you don't want the drain to push back up). Then check for level, if it has to be adjusted, you could play around with it until its level. The important thing is to have at least most of the mortar under the drain before you set it, you could pack some more after if needed.

[alember]

Thanks Matt sounds good

but I'm still nagged by the following:

If I recall correctly, Schluter Kerdi has been around for about 15 years and the Kerdi Drain for about 5. Which means there's 10 years of Kerdi being used without the Kerdi Drain. What was the method? Anyone know? Does Schluter really turn away folks who already have a standard shower pan and want to use Kerdi on their walls?

The reason's I persist in possibly using my current drain is that:

First, I'm about as sure as i can be that the current drain assembly is as solid and water tight as it can be and that when I do a leak test, at least the connection between the drain and the U-trap isn't going to leak. The second is that there is the possibility of this shower being inspected, and where I am and the building I'm in, I've been told that by code, no part of the plumbing system can be made of PVC. And even if everything is all closed up, the one part that the inspector can still see is the drain. I don't know how strict they are but it seems to me that if possible, I should try to follow code.

I'm in Manhattan in a prewar fireproofed building.

Thanks again

al

[cx]

Welcome, Al.

As you have surmised, it is possible to use Kerdi (or similar membranes) with clamping drains. I've never done it, so I'm not familiar with the nuances. We have people here who do know, so just stand by for more info. I do know that you really want to use that Kerdi drain if at all possible.

If you think you may have a problem with your local inspector about using a PVC or ABS (Kerdi comes in either) drain, I would certainly talk to him before you proceed further. Inspectors are almost universally more apt to grant permission than forgiveness in my experience. But the first thing you're gonna wanna axe him about is building the Kerdi pan in the first place. Apparently it is not universally approved by local building codes.

Stand by for more good news.

[Ron]

Hello Al

I used to use the Kerdi membrane on shower pans before they came up with their own drain assembly.No written specs on how to do it correctly.

Here's how I did it with confidence.

Cut the Kerdi membrane to fit over the drain's screw holes(for the chrome cover)and make a perfect hole to match the drain's opening.Adhere the Kerdi with thinset only on the mortar bed,not the drain.Use a poly-urethane caulk to glue the membrane to the top of the drain assembly.Has to be polyurethane like Sika Flex or similar.Make sure that it covers the area 100 %.Then get some gasket material and cut pieces as rings to make up a thick spacer to raise the chrome cover to the height of the tile.Buy some longer trim screws too.

I've done about 10 of these.Most of them relied on the Kerdi membrane as the sole waterproofing.None of them have failed.

I've used their drain,of course,since they came out.

[Ron]

Good point,CX,about the inspector.We don't have these guys lurking around where I work.

[kevreh]

Originally posted by MHI
Hi Al,

I would be best to get rid of the cast iron if you want to use the kerdi drain. There is no way to combine parts of both.

I'm not a professional plumber, but the only way I can think of is to use a rubber adaper (the ones where you tighten around it with those metal bands) to connect pvc to the cast iron. Then you glue the drain to the pvc.

As someone else mentioned, maybe you can get permission ahead of time?

I wonder why you can't use pvc there (in Manhhatten). Must be a union/job security thing.

kevin

[MHI]

Al,

I didn't know where you were from. In Manhattan, the code is for cast iron drain pipes in multi family dwellings. I believe the code is for noise reduction.

Kevin, when I said to get rid of the cast iron, I meant the drain assembly, not the whole piping system.

If you got permits, though, I would check about the kerdi drain.

[alember]

Thanks guys

Matt and CX, for reason's I don't wish to get into, a consultation with the inspector is not possible. That he might inspect at some future date though, is quite possible and that lack of forgiveness that you mention CX is what I'm worried about. But living with my old, floor rotted, drywall collapsing shower was also not possible.

Ron, I have a different style drain than the one you mention. The Chrome part of my drain actually screws in to the cast iron part. And the part that would be even with the tile rests considerably higher than the clamping ring - as it is expecting that second layer of mortar. It looks like the drain in this thread, though it is made of cast iron:

http://johnbridge.com/vbulletin/show...ast+iron+drain

[Ron]

Aaah,so the piece that screws in doesn't have a separate chrome cover that is fastened into that with 2 trim bolts?I see.

Is there any way to use the aforementioned Fernco style coupling with the cast iron so that you end up with a 2" ABS pipe that is below the subfloor by about 1 1/2" ?If so,then you can incorporate a proper Kerdi drain flange.

[alember]

Yes, I could (I think) use a cast iron to PVC or ABS adaptor without raising the drain height too much and then use the Kerdi drain. But as I mentioned earlier I have various reasons for being cautious about going that route.

Like other do it your selfers I've seen on this site, I tend to be exceedingly meticulous (perhaps part of what is required to not only "do it yourself" but to also end up on a site such as this) and like to explore all possible avenues before gingerly (but happily) proceeding down the one that seems best for me.

I believe Noblevision has a system for doing exactly this - using a traditional shower pan with a membrane which goes over the inside of the CBU. Except their membrane isn't vapor proof and you get into the whole sandwich thing of having a vapor barrier behind the CBU with the waterproof membrane in front which I'm not comfortable with.

I also get the feeling that Kerdi is easier to work with. And since they are such an innovative company and constantly searching for new solutions, I can't help but wonder what their solution was before they had their drain and if it was any better than Nobleseal's current solution.

I know this issue has been discussed at some length in these forums but the outcome always seems to be, use the Kerdi Drain or go with Nobleseal's solution but which, because it allows the bed to become saturated, isn't as good as Schluters.

By never explaining how to use the product without the drain (although it was used without the drain for 10 years) this approach (by Schluter and by the pros who advocate Kerdi on this site), seems more of a marketing one designed to encourage the use of Kerdi drains (and rightly so if you can use one).

But if you can't, or you don't want to, what then is the answer?

I'm looking for someone, (like you Ron), who through thought and trial might happen to know the best way to do this and is willing to share such knowledge.

Thanks

al

[John Bridge]

Hi Al,

It's possible to just use a pvc membrane in the clamping drain and do a conventional mud floor. You can still use Kerdi as your waterproofer on the walls and ceiling.

That way, you can have your inspector check the pan when it's filled with water in the usual manner.

The complete Kerdi system is the best, of course, but if it means re-inventing local laws it's not worth it.