Back-to-back toilet installation

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by JRGlynn, Dec 19, 2009.

  1. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    My house was built in the 60s. It has two upstairs bathrooms and the toilets are installed back-to-back. The waste lines are copper and bronze!

    One of the toilets has had a long standing leak problem. I've just ripped out the entire bathroom floor down to the joists and it looks like the installation has been "repaired" at least four times over the years. I'm preparing to replace the floor and purchase/install a Toto Eco Guinevere toilet. I want to make sure that MY installation does not leak!

    I notice that the installation instructions recommend a "double sanitary tee-wye only." I wonder if water flowing up from the other toilet may have contributed to the leaking problem... I can't see the current wye, but because of the age of the house, I strongly doubt that this type of wye is currently installed. Do I need to tear into the rest of the plumbing installation to replace the wye?

    BTW, the downstairs bathroom appears to be on the same stack.

    Thanks for your help!
    JRG
  2. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    [​IMG]
    This is a double fixture fitting.
    Even with these, the water can skip across, pushing an air column toward the other bowl, which then causes loss of water in the other bowl.

    I'm more inclined to not install a cross fitting, but instead wye off lower in the wall and come up twice. Once for each toilet.
    The two vents would then revent at 42" above the floor.
    Or you can use a douby "wye" fitting, which prevents the water from the flush from "skipping" over the opening.


    [​IMG]
    Here is a section of 3" copper pipe that I pulled out of a home in Somerset.
    It was on a toilet waste line.

    Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

    [​IMG]
    Last edited: May 5, 2014
  3. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    Ouch! I hadn't considered that the waste line itself might be leaking.

    I understand about Y-ing out lower in the wall, but I don't understand about reventing 42 inches above the floor.

    It sounds like this would also require repositioning the toilets to offset them from side to side. Correct?

    Thanks again,
    JRG
  4. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    A fixture cross supplies two fixtures using one vent.
    If you don't cross it, then you have two vents.
    Those two vents would tie together above the flood level of the highest fixture.
    If a kitchen sink is nearby, that would be 36" plus the required 6" making it 42"

    The toilet wouldn't have to move, they could have easily been plumbed in those locations without using a cross.
    It's just a matter of how they are run.
    You can use a fixture cross, but the water does run up the other arm, forcing air into the bowl, which surges the water up the bowl, and then over the trapway.
    You wind up losing a bit of water everytime someone flushes in the other room.
    I have some nice video I took with the toilet off, it's pretty funny to watch.
  5. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    Normally in Bellevue, you would revent the downstairs plumbing above the upper floor plumbing.
    I think you left a few things out in the drawing.

    [​IMG]
  6. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    Interesting. This is all original construction, which I "assume" was inspected when the house was built.

    It's hard to tell what my venting really looks like, because it's all in the one wet wall. If the venting is as I describe it, could this cause or contribute to the leak problem that I'm trying to fix?

    If I simply replace the one upstairs toilet that I removed with a Toto Eco Guinevere and "assume" that the venting is correct, what kind of trouble am I asking for?

    Thanks,
    JRG
  7. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    The Eco Guinevere has been working fine here.
    I've sold 120 of these bad boys in the last two years.
    You have until the end of the year to get the $100 rebate from Cascade Water on these.

    If you have a leak, it would be from a wax seal most of the time.
    On the Eastside, most installations need two wax rings,
    The flange is installed on the 3/4" plywood, and then the flooring is installed around the flange, making the flange too low.

    The Fluidmaster Waxless seal works well on the adapters too.

    The flange below was raised before the flooring went in.
    I was able to single wax with this flange, but unless the flange is "above" the finished floor, it will take two wax rings.

    [​IMG]

    [​IMG]
    Installed and ready to be caulked at the floor.
    Last edited: May 24, 2014
  8. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    Here are some details of my existing flange and piping. As you can see, I've removed the rotten floor and I'm down to the joists.
    20091221_ToiletFlangeDetail (1).jpg
    20091221_ToiletFlangeDetail (3).jpg

    I'd like to replace this flange and raise it to sit above my finished floor. Do you have suggestions about how to do this?

    Also, can I buy the new toilet from you and get the rebate?

    Thanks,
    JRG
  9. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    You could unsolder the flange, and use a longer section of pipe there,
    or use a copper by ABS Mission coupling and run it in ABS

    Can you post a picture of the cross fitting you are using back there?

    Also, I have the Eco Guinevere in stock here, and Mike at CascadeWater. org sends out the rebate checks.
  10. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    Here's a picture of the cross fitting. Do I need to replace it?

    20091221_T-Fitting (1).jpg

    I'll give you a call around 9 AM tomorrow to order the toilet.

    Thanks,
    JRG
  11. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    That fitting should be replaced.
    When you phone tomorrow, we'll talk about it.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,607
    Location:
    Cave Creek, Arizona
    fitting

    It should be replaced, but I doubt that YOU can do it. They do not make a brass back to back fitting, so you would need a double combo. IF you can find one, be prepared for a major "sticker shock" when you see the price. It might be your first clue as to why they did not use it. ALL of your drawings, including the one showing your existing installation, would be rejected in this area, and also any that I have been associated with for the past 60 years.
  13. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    [​IMG]
    The plumbing above, with the toilet on the right,
    and then below looking from the other direction, the stack for the toilet on the left.

    [​IMG]
    The existing piping for the bathroom

    [​IMG]
    Next, cut out the old Sanitary Cross.
    Last edited: Dec 24, 2009
  14. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    New Eco Guinevere toilet

    [​IMG]
    Above, it looks like this, the one toilet is straight back from the stack,
    the toilet in this room is offset and angled back to the previous location.

    [​IMG]

    Replace with a Sanitary tee for one toilet,
    And a Low heel Santee for the other toilet.
    This way, both are vented, and the flush is forced down instead of across and toward the other bowl.

    [​IMG]
    The 2" pipe toward the right is the downstairs plumbing vent.

    [​IMG]
    And the New TOTO Eco Guinevere
    Sweet!
    Last edited: May 24, 2014
  15. JRGlynn

    JRGlynn DIY Junior Member

    Messages:
    7
    Location:
    Bellevue, WA
    Thanks Terry. Nice pictures :)

    That cpvc U was a temporary fix to a tragic SawsAll accident when I was removing the wallboard. It only needed to last until your crew showed up, but it leaked anyway...

    We're very happy with the new installation, particularly because it is now the only working toilet in the house! When I removed the downstairs toilet, I found more rot, so I ripped out the floor from that one too. I have replaced the sub-floor, but I still need to install the underlayment and some acrylic tile before I can install the 2nd new toilet. The third one will be installed some time next week. I get to take the Christmas day off!

    Thanks again,
    JRG
  16. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    Another Back to back toilet installation Question

    Rather than start a new posting (can't figure out how to do that here!), even though this thread is very old, I just wanted to ask a question on basically the same situation. My house is 40 years old, and has 3 inch copper main stack which runs from the basement floor up through the first and only floor, then up through the roof. It has the brass cross setup with 2 back to back toilets which never had any problems. THIS cross, in addition to the 4 3 inch connection, also has 2 1 -1/2 inch inlets, one on each side of the cross which receives waste from the bathtub and lavatories on the main floor. Never had any problems in the forty years we have live here, knock on wood.

    Now, I am going to remodel one of the bathrooms and replace the Kohler Rialto toilet with a new Toto Ultra Flush or Drake. Reading this thread made me look real closely at how the drain system is plumbed, and I see that although one toilet (the Rialto that is being replaced with the Toto is what I guess the normal distance from the main stack with a probably 15 inches from the cross to the center of the toilet flange, and the other toilet on the other side of the partition is about a little less than 5 feet from the stack I haven opened up the walls enough yet to get a tape measure in there, for a total distance of real close to 6 feet from the center of one toilet to the center of the other toilet. As I said previously, we have never had a problem, be it a clog or anything related to the main drain. I read somewhere else that if the distance from one toilet to the other is 5 feet or more, the water jumping from one toilet across the cross and affecting the other toilet should not be a problem. Any professional opinions on this? I can't seem to find the site again that I read this to link it. Thanks!
    Last edited by a moderator: Apr 1, 2011
  17. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    IMG_9803.jpg Here is a picture taken from an access panel opening in the basement looking up at the very busy main waste stack which goes all the way up through the roof as the primary vent. There is another vent for the kitchen sink about 12 feet away from here which isnot in view. In this shot, you can see the two toilet bends. The white PVC bend is a replacement I put in about 10 years ago to replace the lead bend that cracked at the toilet flange, and is where the new Toto Drake or Ultramax is going. The lead bend in this shot is from the old Eljer toilet in the other bathroom. The framing in this photo shows some really old studs that I used about 35 years go to form a wall. These studs came from old torn down apartment houses in Brooklyn, NY with lath and plaster walls. Back then "re-purposing" was not a word, but I used them because buying new studs was over my budget back then. Really.
    Last edited: Apr 3, 2011
  18. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    From th eother side of that wall

    And a view from the Other side of the cross fitting

    Attached Files:

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  19. Terry

    Terry Administrator Staff Member

    Messages:
    14,994
    Location:
    Bothell, Washington
    With the cross, flushing one toilet is going to surge across the cross and force a bit of water from the opposing bowl.
    I have something similar in my home, but with a fixture cross, not a santee cross. Mine still pushes water out of the other bowl. Not a big deal, but it does happen.
    Since you have a bit of room to work with there, if there is too much of a problem, you can cut some out and do a little reroute too.
    When I pull my basement ceiling out below the upstairs bathrooms, that's what I'm going to do.

    They do make a Mission band for going between 4-1/8" OD copper and 4-3/8" Plastic pipe. We don't use the rubber fernco like you are using. That's a Home Depot, "I've never done plumbing" fitting.

    Here is the way I rerouted that other bathroom, using a Mission coupling for the transitions.

    [​IMG]
    Last edited: Apr 3, 2011
  20. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,792
    Location:
    Long Island, NY
    Thanks Terry. I am going to go ahead with the demo of the bathroom, hopefully this week, and if there is a real problem with this setup and one toilet affecting the other, then I'll do a reroute of the piping from the toilet closest to the stack to a point just below the Wye already there below the cross that takes the 2 inch line from the kitchen. Bye the way, it looks roomy from that photo, but I may have to opeen up that wall that has those antique studs in them.
    And I will use the proper coupling in any case, because the toilet I am replacing at this time is sitting on a one inch marble piece that I guess they used here by code when a toilet is on a floor other than ceramic tile. This bathroom has vinyl tiles since 1971, but I am putting in ceramic tiles now. The other bath was built with ceramic tiles and did not have a marble slab under it. I often wondered about the marble, but never asked a plumber or the town building dept. about it. Is/was that common to use a marble slab? :confused:

    Bob
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