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Thread: Convert single toilet to two back-to-back toilets

  1. #1
    DIY Junior Member phxphun's Avatar
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    Default Convert single toilet to two back-to-back toilets

    And now for something completely different...

    I'm converting a single bath room into two smaller baths. I'd prefer to avoid having to do any demolition of the concrete floor. I'm building the wall between the two rooms, so I can do whatever I want with it. The new wall happens to line up with where the exiting toilet drain is.

    So, I'm wondering if I used two wall-mount rear-discharge type toilets, would it be possible to have them both discharge into the exiting toilet drain if I centered the wall directly over the drain? Seems a little nuts, I know.... but I was thinking I might be able to adapt two in-wall tanks, mounted side-by-side inside the wall to provide water to each toilet. Or if that's too complicated, I could opt for wall-hung, back-outlet toilet models that have the tank on the wall, like the American Standard Glenwall .
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    Would there be a way to configure the plumbing connections for both toilets to the single drain? Can someone tell me if this is even remotely possible? Here's rough idea...
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    Retired Defense Industry Engineer jadnashua's Avatar
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    If you research a little, you'll find some discussions about back-to-back toilet problems when the proper configuration is not done. Today's toilets flush MUCH faster than the old ones, and the waste from one can skip over into the opposite one unless the layout is not done VERY carefully. You need to also consider that the carriers for these toilets, especially back-to-back would require the wall to be VERY thick, and take up a bunch of room for your two small bathrooms. So, could it be done? WIth a thick enough wall, yes. Is it really practical? Maybe not. Would tearing up the concrete and replacing the fittings for two toilets work out probably better? I think so. Be interesting to see what I may have missed in other (hopefully) commenters thoughts.
    Jim DeBruycker
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    DIY Senior Member wjcandee's Avatar
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    If there's a 12" rough-in on the original toilet, then he's only going to have 12" from center to wall on each of his back-to-back toilets. If he needs a permit (and you would where I am if you are erecting a wall and doing plumbing), he's going to fail the inspection for not being 15" from centerline to the wall on the lateral requirement.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Is this residential or commercial space?

    It's doable. You will be breaking concrete though. How much is yet to be discovered. I see that you've already drawn in the thicker wall that the wall hung bowls will need. If this is handicap, then the centerline to wall will be 18"

    I've replaced old gravity wall-hung bowls with A/S Glenwalls on the back to back fittings. It works. Many commercial bowls are done that way with cast iron carriers.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Use a back to back resiidental wall hung carrier and two Glenwall toilets. The wall will have to be 8 1'2"minimum finish to finsih, but can be greater if necesary.
    Licensed residential and commercial plumber

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    DIY Senior Member wjcandee's Avatar
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    I'm assuming that you aren't looking to create something super-schwanky, because I suppose one other option is to leave the wall on the thinner side and use something like a Geberit Monolith for the tank and connections. (The Monolith is a black-glass deal that has the tank and carrier already inside and sits on the outside of the finished wall.) The whole thing, including tank and carrier but not bowl, will set you back about $700, which is about twice the cost of a Geberit concealed tank and carrier. Or, I suppose you could put one of the carriers in the regular-size wall, and the Monolith in only one of the bathrooms; I don't know if you can get them back-to-back that way, though, although it may be possible if you're inventive. Might be worth it if the space in the room is real important to you...



    Also available in white and, now, "mint". You could mount a nice Toto Aquia or Maris bowl on there and it would look nice (and be further off the ground than the item shown.)
    Last edited by wjcandee; 02-12-2013 at 06:22 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    SHeesh...I said it was doable, but at the cost of a much thicker wall. Easier, and lots more choices of toilets, would be to tear up the concrete and create the two flanges for regular floor mounted, stock, 12" rough-in toilets.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Forum Admin, Expert Plumber Terry's Avatar
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    Easier, and lots more choices of toilets, would be to tear up the concrete and create the two flanges for regular floor mounted, stock, 12" rough-in toilets.
    This is the way most plumbers would see it.

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    Quote Originally Posted by jadnashua View Post
    SHeesh...I said it was doable, but at the cost of a much thicker wall. Easier, and lots more choices of toilets, would be to tear up the concrete and create the two flanges for regular floor mounted, stock, 12" rough-in toilets.
    Quote Originally Posted by Terry View Post
    This is the way most plumbers would see it.
    I concur. Concrete doesn't scare me. Just skip the gym that night.

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