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Thread: Quick ? re PVC-Kerdi drain splicing through concrete

  1. #1
    remodel contractor/top shelf craftsman painter jordanski's Avatar
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    Default Quick ? re PVC-Kerdi drain splicing through concrete

    Hi everybody, great forum!

    I've got a quick question but one that makes me a little nervous and want to get it right.

    Re-doing my shower with tile, hardibacker walls and using the Kerdi drain kit with pre-fab slope and dry pack mortar for the floor, whole thing gets the Shluter waterproofing flannel then tile, pretty solid idea what to do on the tile end.

    The existing floor is a 4" basement pour with 2 1/4" pvc vertical drain pipe going down to the P trap. Drain was originally off-center so I had a very good plumber chip up a hole in the concrete and center a new drain, which was a standard pvc drain made for tile. Was going to do that with an old school mortar pan. Mid-project got sold on the Kerdi drain/pan system which all the pro tile guys I know have switched to using.

    So I need to:
    1. cut the vert pipe, glue in a coupler piece and a short section going up to the new kerdi drain piece (which is also pvc), and glue that to the new drain flush with the floor.
    2. patch the concete hole (about 10" wide by 3' long), then skim coat and build the pan slope

    My question is: The splice on the vertical pvc drain pipe will go directly through the concrete, do I need to wrap the pipe in 1/4" foam before I patch the concrete? I've got differing and dubious advice on this, hoping someone can give me the final word on this. I live in seattle, so we have big differentials in moisture through the seasons but rarely deep long freezes, if that matters.

    thanks in advance for any help on the matter,
    jordan

  2. #2
    Homeowner geniescience's Avatar
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    PVC splice, in new concrete?

    Is that your question? Whether PVC needs an insulator to prevent new concrete from touching it?

    Whether the drain is from one company's shower kit or not is irrelevant.

    David

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    In a wood floor, Schluter wants a 5" diameter hole in the subfloor to accommodate the drain. The funnel in the drain is fairly large before it tapers down to the 2" drain connection. So, your hole in the concrete around the flange needs to be big enough to accommodate it. You can pack that area with deck mud once connected to fully support the drain.

    For those who may never have seen the Schluter Kerdi drain, it has a large surface area with a shallow well where the grate is attached. It allows flexibility in location of the grate (which is about 4" square). The top material of the drain has a special surface that accepts thinset well to mate with their Kerdi waterproofing membrane. The membrane has a fleece on both sides to embed into the thinset to hold it in place and to hold the tile with the thinset. It is also hygroscopic (water resisting), so the junction when installed properly with enough overlap, prevents water infiltration through any joints. Neat stuff which puts the waterproofing layer directly under the tile which means the whole shower dries out much faster.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Homeowner geniescience's Avatar
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    Default no special treatment?

    Kerdi being made of PVC does not require any extra special handling in concrete compared to any other PVC.

    Is there a caveat to be aware of, when concrete touches PVC, or a PVC joint or splice?

    david

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    If it is designed for intimate contact with thinset, I don't see where straight concrete would have any affects...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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