My PVC Membrane Leak Test Failed

Discussion in 'Shower & Bathtub Forum & Blog' started by ejacobson, Mar 20, 2008.

  1. ejacobson

    ejacobson New Member

    Dec 2, 2005
    My plumber finished roughing in my plumbing and talked me into letting her "fold the shower pan", which in her case means, laying a sloped bed on my subfloor and framed shower, and folding and attaching the membrane. She used orange IPS Water Tite PVC 40. We left the drain plugged and about 15 hours later I noticed a significant amount of water leaking out onto my subfloor from under my curb. I could also see water soaked into the subfloor from the drain (looking up from my basement).

    Here is a picture of the membrane full of water and the wet area after I took it apart.

    I called the plumber and she said it must have had a pin-hole or something. She said she would come back in a couple days to fix it.

    In the meantime, I ripped out the membrane and vapor barrier to let the plywood dry out. I stuck a dehumidifier in there to speed it up.

    It's frusterating, I showed her the Michael Byrne Mortar Bed Shower Floor guide and she said it was way overkill.

    What's my question? I'm not sure. I guess I'm wondering if I should trust her to do it the same way and if this is a normal problem. The plumber has some 40 years of experience but I'm still kind of upset with what I think I see because I would have done more meticulous work.

    Should I do it again myself or give her another chance?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    Folding the membrane is a common way of doing it. Why did you tear the membrane out? It might not have been defective, other than a possible leak at the drain connection, unless someone punctured it.
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Code requires the waterproofing layer to be sloped, so any moisture that gets there can flow to the weep holes in the drain. Overkill? No. Mortar is alkaline. Eventually, with contaminants (soaps, body oils, cleaners, etc.,) it will turn acidic. Once that turnover happens, the shower pan will start to smell like a swamp. Do you want that?

    Industry standards require that pan to be on a presloped bed.

    Often, all the inspector wants to see is that it doesn't leak, and are doing a great disservice to the people they are paid to protect.

    If you want a long-term, successful result, demand it be done to industry standards.

    If you want some help to see what those are, there's some really good info at They'll set you straight.

    If the plumber didn't use the preformed corners or notch the studs so there is extra room in the corners, you will have trouble getting the cbu to lay flat without bowing. This makes it nearly impossible to have a straight wall. You can get the details on that linked site. Also, over a plywood floor, the mortar layer should have lath installed. This puts the metal on the wet side of the liner. The lath will eventually rust, swell (rust is bigger than elemental iron), and break the bond in the setting layer. Lath needs to be on the dry side of the liner - in the preslope.

    These failures take years...well beyond the typical one-year warranty most contractors give. You'll want it to last longer than that...demand it be done per the industry standards - you need to know what they are.
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