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Thread: moving shower drain

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  1. #1

    Default moving shower drain

    Hello Plumbers...Im a homeowner redoing my bathroom and am looking for advice on moving my second floor shower drain. I am expanding my shower by 1 foot or so and want the drain in the center of my tiled shower floor, so I will move it approx 6 inchs.

    I pulled out the existing drain and looks like I have no obstructions where i want to move the drain.

    Do I just open up the subfloor and cut the ABS pipe before the P trap and extend the drain the 6 inchs? I guess I need to be concerned about the slope...1/4 inch more slope for this 6 inch move??

    Another question...I bought a cast iron drain from Home Depot...I will hop mop (in calif, thats what most do here), I take it, the bottom 1/2 just slides over the 2 in abs pipe, and the little "dog ears" keep the drain from moving because its locked into place from the wood subfloor.....but, do i place the drain ontop of the subfllor or ontop of the preslope that i will use on the subfloor? My hot mopper will use a 1/2 preslope material that will go under the hotmop..this makes it easier to have the tar presloped.....so, bottom 1/2 of drain over or under the preslope material??
    Thanks in advanced,

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


    Note one important item...the drain has weep holes in it that can easily be clogged while hotmopping. These allow any water that gets through the grout, cracks, etc. in the floor of the shower to run down the preslope, and down the drain. Make sure that those are clear prior to tiling. Don't know about the other questions, I'm not a pro. I guess, done absolutely right, a hot mop can work out. The people at www.johnbridge.com (a friend of Terry's) generally think otherwise. You could ask your question there and get some other opinions. I don't think that the tile association of America approves hotmopping, but I'm not sure. Doesn't mean it can't work, but it is not an approved method by that body. Your local inspectors are the final decision on what is allowed, though.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    The bottom half of the drain goes on the subfloor. Then the preslope and then start the hot-mop. Be careful of the weepholes; and you are using at least 3 layers of hot mop, right? I believe that is the minimum allowed.

  4. #4


    Thanks guys...I love this site, you are great for the DIY's.

    One more question...im moving the shower drain 4-6 inchs so it will be centered....the drain pipe comes right under a floor joist and this is where the P trap starts....will it be ok to cut the pipe right before the Ptrap, then just add a 4 inch or so piece...then add the P trap? If I did that...I would not be doing anything different to the pipe slope??

    If this doesnt make sense...I guess im asking if i need to add more slope to the pipe slope for an extra 4-6 inchs...

    Thanks !

  5. #5

    Smile Hot Mop

    If you are in southern california there is a great company that hot mops, they are called DK Shower Pans, you can reach them at 866-305-4980, they are very helpful and have a very good turn around time. I have been told also to never buy the home depot cast iron insta-set drain. The tool that they supply is very awkward for tightening the bottom flange onto the ABS pipe and they usually end up very loose. You should go to a plumbing supply store and purchase an instaset drain that has the 3 bolts to tighten the bottom piece onto the pipe instead of the tool that home depot drains supply. There is a great website that gives details and pictures of how to prep for the mop, it is www.tiledoctor.com, it will also show how the drain needs to be correctly set.
    Last edited by battery04; 05-17-2005 at 06:51 AM.


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