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Thread: DWV Piping Dilemma from Adding wall-mounted toilet on one side of back to back setup

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  1. #1
    DIY Junior Member DIY_Steve's Avatar
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    Default DWV Piping Dilemma from Adding wall-mounted toilet on one side of back to back setup

    Hello everyone,

    I'm getting into a remodel of our small master bath in our 5br/3ba home. The master bath is very small so we have decided that a wall mounted toilet would really benefit the small space with the extra room it frees up. We selected a geberit carrier and duravit toilet but thankfully haven't ordered them yet. I have completed the demolition and discovered I have a couple of problems:

    1. There is a 4" CI vent that runs vertically through the wall right where the carrier should go. Connected to this 4" vent are all three bathrooms, so that is 3 toilets, 2 showers, one shower/bathtub, and three sinks. My first thought was no problem, I will just add a sanitary tee or wye that routes the vent stack around the carrier and picks up all of the other vents in the process. This would have been great except for the next problem:

    2. The other bathroom on the main floor is right through the wall from the master bath, so that the two existing floor-mounted toilets are back to back and connect into a 4x4x4x4" double sanitary tee below the floor. The top of this tee is the 4" vent stack. So if there was such a fitting as a 4x4x4 "ninetytee" where the two side inlets were offset 90 degrees instead of 180 degrees I could solve this problem again by routing the vent stack off to the side of the carrier, but as far as I know no such fitting exists?

    So I have come up with a couple of brainstorm solutions but I don't know if products exist. Your help with these possible solutions or any others you may have would be much appreciated:

    Brainstorm solution 1: If such a thing exists (google doesn't seem to think so) I would put a carrier in the wall that serves a toilet on both sides of the wall off the one tank. Downside here is I have to buy another wall mount toilet, and I don't know if one tank can flush two toilets without problems? Does code even allow it? Am I missing any other problems this would create?

    Brainstorm solution 2: I could replace the 4x4x4x4 Double Sanitary Tee with a 4x4x4x2 Sanitary Tee With Right Side Inlet and then route the 2" Side Inlet up and around the carrier as the new vent pipe. Questions here is if the 2" vent pipe is big enough for the two toilets on the main floor and the third directly below in the basement? I could run some of the other sink and shower vents through the roof or attic independently if necessary rather than joining them all back into one like they are now. If I use the long radius elbows on the 2" vent pipe does it still serve its function okay? Does code allow this sort of alteration?

    Brainstorm solution 3: I spotted this fitting called a Vented Closet Tee - Right - With 2" Top Vent. It looks like if I could bring the floor toilet into the side and the wall toilet in from the top and then route the vent around the wall carrier this might work. Not sure if there is enough space between my joists to do this (about 14")? Why are some of the closet tees baffled and some not? Does code allow?

    Any other solutions I haven't thought of???

    Thanks in advance!
    DIY_Steve

  2. #2
    Moderator & Master Plumber hj's Avatar
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    You are really trying to do something you do not have the experience to do.
    1. If it were even possible to have one tank for two toilets, it would need to be double the water capacity because BOTH toilets would have to flush at the same time.
    2. Taking the vent off the side of a tee and then having the wall hung toilet flush past it would violate every code and principle of plumbing.
    3. I do not remember ever seeing a baffled closet tee, other than with a So-Vent system. The closet tee you are referring to is the way to flush one toilet past others on a lower level, but it usually means the lower one will be offset about 5" from the centerline of the stack. I have never seen or worked on an actual Gerberit wall hung, but most of them have the tank in the wall so your pipes would have to offset around it.
    Licensed residential and commercial plumber

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    DIY Junior Member DIY_Steve's Avatar
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    Hello HJ and thank you so much for your input. See below for a few specific follow on comments/questions.

    "You are really trying to do something you do not have the experience to do. "
    You are right about this, thats why I'm on this forum asking questions :-)

    "1. If it were even possible to have one tank for two toilets, it would need to be double the water capacity because BOTH toilets would have to flush at the same time."

    This is what I figured so I will scratch this idea - too expensive anyways...

    "2. Taking the vent off the side of a tee and then having the wall hung toilet flush past it would violate every code and principle of plumbing."

    So why is this, does the vent always have to be completely above where the toilet flushes past? If its not above what is the problem that occurs?

    "3. I do not remember ever seeing a baffled closet tee, other than with a So-Vent system. The closet tee you are referring to is the way to flush one toilet past others on a lower level, but it usually means the lower one will be offset about 5" from the centerline of the stack. I have never seen or worked on an actual Gerberit wall hung, but most of them have the tank in the wall so your pipes would have to offset around it."

    I was looking at the Charlotte Pipe PN463 but I see now that only the cross has the baffle which makes sense, the Right Closet Tee PN 457 is what I'm thinking of. The way the Geberit works is it flushes into a downward 90 so its sort of on an upper level compared to the floor mount toilet in the other bathroom but only by about 12". Thats why I'm thinking that if the wall toilet comes into the top of the closet tee and the floor toilet comes into the side, and I route the 2" top vent upward through the roof, this setup might work? What do you think?

    Thanks!
    DIY_Steve

  4. #4
    Moderator & Master Plumber hj's Avatar
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    quote; So why is this, does the vent always have to be completely above where the toilet flushes past? If its not above what is the problem that occurs?
    The water flowing past it, negates the vent and makes it useless.

    The 457 is the proper fitting, but technically, if you just turn the Gerberit down into the top of it, the inspector may not consider the wall hung toilet to be vented. You also have to figure out how to get the floor mounted toilet's opening back where it is now.
    Last edited by Terry; 11-28-2012 at 08:49 AM.
    Licensed residential and commercial plumber

  5. #5
    DIY Junior Member DIY_Steve's Avatar
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    Quote Originally Posted by hj View Post
    The water flowing past it, negates the vent and makes it useless.

    The 457 is the proper fitting, but technically, if you just turn the Gerberit down into the top of it, the inspector may not consider the wall hung toilet to be vented. You also have to figure out how to get the floor mounted toilet's opening back where it is now.
    Great thanks again for your input hj I really appreciate it! So I understand on the side inlet fittings why they don't work for a vent, probably why they are named side inlet not top vent after all!

    So I do understand that the floor toilet which is lined up on the CL of the cross will now have to line up with the new CL of the closet tee. It looks to me like I can solve this with a 22.5 fitting on the closet tee inlet and then turning the flange under the floor toilet to line up. Luckily where this all sits in the joists there is room to do it. Does this solution make sense, do you think it will work? Am I missing anything here?

    My next question is then if I get my closet tee in the no hub CI configuration (they are only available in CI as far as I can tell) and put it inside the existing bell on the existing drain pipe that is under the sanitary cross that I will replace, is that possible? ie will the existing fitting come out okay without damaging the existing pipe/bell? And then from there can I use ferncos off of the CI and go to ABS or PVC?

    Thanks in advance for your continued help! This one is pretty complicated so I may just have a pro plumber do it for me, but want to make sure I'm not "taken for a ride" in the process...

  6. #6
    Moderator & Master Plumber hj's Avatar
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    You cut the existing cross out and replace it with the 457, then make your connections to it as necessary. IT can be a daunting task for a DIYer and HOW will you know if you are being taken for a ride, unless you get multiple estimates? You CANNOT use "Ferncos" as you are probably using the term for at least two reasons.
    1. They are not permitted INSIDE a building, and,
    2. The cast iron fitting is very heavy so you need connections that will stabilize it.
    Licensed residential and commercial plumber

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