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  1. #1
    Join Date
    Mar 2013
    Posts
    3

    Default Need Help!! Back To Back Toilets

    I have renovated most of our home myself with minimal difficulty but I have seem to run into a wall here. I want to make a new 1/2 bath (toilet and sink) which will serve the master bedroom. The space for the 1/2 bath is directly behind an existing bathroom. I want to install a toilet in line with the existing toilet. There is a 3" vent pipe running up through the roof. This vent will be between the two toilets. The toilet flanges will be approx. 30" apart (center to center). Both toilets will be on the same drain pipe which is under the concrete floor. The new toilet will be between the old toilet and the septic tank. I have cut the floor and the pipe is exposed and waiting for me to cut into it and install the new pieces. This is where I become lost. I am getting conflicting advice from many sources and I'm not sure which is the proper method to use. I almost installed a 3" saddle tee today but just don't feel right about it because the direction of flow is a direct 90 degrees into the drain line. When the toilet is flushed shouldn't the sanitary tee flow toward the septic tank? Will one toilet cause problems for the other being installed so close and on the same 3" drain? I'm also not sure at what point to install the flange. Should it be on top of the tile floor or on top of the concrete. If it's to be installed on the concrete should the toilet be installed on top of the tile or should I install the toilet on the concrete and then tile around it? I know, I know, what a rookie, but I'm determined to do the job correctly the first time. Any advice you can give me will be greatly appreciated.
    Let me recap the install and direction of flow: Existing toilet --> 3" drain pipe under concrete --> 3" vent pipe in wall between toilets and through roof --> new toilet directly over 3" drain pipe --> septic tank. Also keep in mind that the two toilets are only about 30" apart.

    Thanks again,
    David

  2. #2
    Join Date
    Aug 2007
    Posts
    6,481

    Default Re: Need Help!! Back To Back Toilets

    I can't answer your questions regarding the 3" line issues, but I can tell you that the toilet flange should be flush with the finished floor height.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  3. #3
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    821

    Default Re: Need Help!! Back To Back Toilets

    you do not want a Tee because of the reason you stated. you need to intsall a 3" Wye. there are differing opinions about the flange. i install them on top of the tile, some people install then flush with the tile. either will be fine. DO NOT install the flange on the concrete and DO NOT tile up to the toilet. tile under the toilet.

  4. #4
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,089

    Default Re: Need Help!! Back To Back Toilets

    The 3" wye - I second MLB.

    The flange - Flush to the tile is good, like spruce suggested.

    Tile under the toilet - yes.

    It's good that you asking, so you don't make mistakes.

    After connecting the wye, wait for the pipe cement to dry, then run leak tests. After connecting the flange run more tests.

  5. #5
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,361

    Default Re: Need Help!! Back To Back Toilets



    More information: http://www.nibco.com/Fittings/Plasti...e-Hub-ABS-DWV/

    EDIT: I re-read your original post and I don't think this would work, since you're dealing with slab-on-grade construction, UNLESS the lateral pipe is deep enough. How far below the floor surface is the pipe?
    Last edited by Fencepost; 03-21-2013 at 01:22 AM.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  6. #6
    Join Date
    Mar 2013
    Posts
    3

    Default Re: Need Help!! Back To Back Toilets

    The lateral line isn't deep enough to use the above mentioned fitting. I am off to the supply store to buy a wye fitting with as long a sweep as will fit.

    Thank you everyone for all of your advice. I'll let you know how I make out.

  7. #7
    Join Date
    Feb 2010
    Location
    South*East
    Posts
    1,168

    Default Re: Need Help!! Back To Back Toilets

    What type pipe do you have under the floor? Keep in mind that nothing will move to allow for the slip of a fitting.

    John

  8. #8
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    821

    Default Re: Need Help!! Back To Back Toilets

    Quote Originally Posted by Fencepost View Post


    More information: http://www.nibco.com/Fittings/Plasti...e-Hub-ABS-DWV/

    EDIT: I re-read your original post and I don't think this would work, since you're dealing with slab-on-grade construction, UNLESS the lateral pipe is deep enough. How far below the floor surface is the pipe?
    that's what you would use for a second floor back to back toilet. since it's on grade, i'm assuming that the current waste pipe would not go straight down behing the toilet. instead it would go down behind the toilet then immediately curve in some direction.

  9. #9
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,089

    Default Re: Need Help!! Back To Back Toilets

    We need to see photos to make an accurate recommendation.

  10. #10
    Join Date
    Mar 2013
    Posts
    3

    Default Re: Need Help!! Back To Back Toilets

    I can't seem to load pictures. Apparently new users need 10 postings before we can post pictures.

    I went to the store and bought more fittings. I think I have got it. The guy that helped me at True Value simply stated that what I am using is to code.

    The 3" line below the concrete is 10 1/2" from the center of the pipe to the top of the concrete.

    If you hear the sound of a jack hammer, you'll know I messed up some how.

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