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Thread: Shower P-trap ontop of slab floor

  1. #1
    DIY Junior Member
    Join Date
    Dec 2009

    Default Shower P-trap ontop of slab floor

    Hello All, I am hoping to install a raised redi tile shower basin on top of a concrete slab floor. However, I do not have the option of drilling into the concrete slab to install the p-trap. I would like to minimize the step up into the shower. Therefore, what is the smallest size p-trap dimension that I could use in order to make the shower base as close to the original floor as possible? I am hoping to direct the waste flow to a water pump contained inside of the wall and towards the existing waste drain pipe. I am not familiar with plumbing regulations... Thank you

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    A shower requires a 2" drain line and trap, so you probably won't like the step-up height. If you can use gravity, that is always the best choice rather than pumping it. You'll have to break the concrete to put a sump pit for the pump, regardless. So, why can't you tear up some more concrete to use a conventional height for your shower? If you can't break the concrete at all, you really can't put in a shower. All of the pumps/basins I've seen (there may be some) require it be below the height of the floor so the water can drain so you don't have the chance of the pump running dry.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona


    You will be lucky to get the drain and trap into less than an 8" step up, and it could be more depending on the drain unit in the shower. ANd that would make the concrete over the pipe so thin, that it might cause a crack in the floor.


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