Toto Wall Hung Outlet Pipe Slope

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Dcommoncents

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Hi, first time poster. Thanks in advance for any help.

I am installing a Toto wall mounted toilet with an in-wall tank system. The system comes with a 90 degree outlet pipe that sits in the bracket. Ideally, I would like to run the outlet pipe horizontally out of the carrier in order to avoid framing difficulties (i.e. floor joists). As I hope the pictures I will (attempt to) post show, the horizontal waste line from the old toilet flange runs under the floor just to the left of the wall mount toilet before teeing into the main stack. It is that horizontal run that I need to connect the wall mount toilet to.

My concern is that, I have not seen these toilets installed with the outlet pipe mounted with an initial slope of less than 45 degrees, and usually they run vertically. Is there any reason why running the outlet pipe horizontally with a 1/4 inch per foot slope would be problematic? I contacted Toto customer service, and they said that a horizontal mounting will cause siphoning of water out of the toilet, but they couldn't explain why, and that makes no sense to me based upon the appearance of the outlet pipe and my admittedly limited knowledge of plumbing theory.

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Terry

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I have no idea why they say that. It seem to remember that someone posted here that they did a horizontal install one time.

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Here is a Gerberit install someone posted. I would have like to see double studs on both sides of the carrier.
 

Dcommoncents

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Thanks. I can't see why a horizontal outlet would cause a problem, where a 45 or 90 degree outlet would not. I hate to glue everything up just to find I'm wrong though. I thought about doing something like what is shown in the Geberit installation picture, but I have very little room to drop vertically or use a 45 before going horizontal -- plus I don't want to extend the hole I already put in my overkill framing which consists of 2 2x8s and 2 2x4s : ).

I did find these two images where people did precisely what I want to do:

However, I don't know if their installations were free of the supposed siphoning problem, nor have I been able to find any discussion on the interwebs that addresses the issue. I have to think this is a somewhat common idea since running the waste lines above the floor seems to be a huge benefit to a wall mounted carrier in a renovation of existing plumbing.

Anyway, I hope someone can chime in to confirm that running the outlet pipe like in the pictures above is either perfectly fine and the Toto customer service guy was pulling that out of his behind, or that there can be an issue and I should just suck it up and change my plan to include a short 45 degree drop. Thanks again.
 

Dcommoncents

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HJ had this to say in a similar thread (https://terrylove.com/forums/index....lly-know-how-to-plumb-them.50618/#post-371118):

A "blowout" bowl would be the ONLY one that would benefit from the 'siphonic action" of a turned down elbow, and they are NEVER used in residences and few commercial installations, except prisons. Once the waste gets "to the wall" it can go in any direction you need to in order to get the pipes installed. ANY "competent" plumber can install these. It is when engineers get involved that it becomes difficult.

To me it sounds like he is saying my horizontal idea will work.
 

sweetChicken

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Any update on your horizontal run solution, Dcommoncents? I have a similar project coming up where the toilet will be against a sloped wall of a gambrel roof with no room in the floor. I want to discharge straight back to the exterior wall then do my thing to drain down and vent up (in fact I could shoot straight into the stack). I know in our office the wall mounted toilets squirt straight back into a mechanical chase separating the Men's from the Ladies'. I found some accessories for the Geberit brand that I think would solve your problem but I suspect it has long been solved. The straight one is the one I would need. Here is the link.
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Dcommoncents

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Sweetchicken:

I did in fact end up using the geberit outlet with the integrated 45 slope you pictured above, which mated with the Toto perfectly. The bathroom isn't fully functional yet (needs tile) and the toilet hasn't been used for #2 yet, but it has flushed quite well many times without issue so I think my solution has worked out. Given my approach, I unfortunately can't give you an answer on the straight outlet you want to use, except to say that I don't think my short slope is doing any siphoning.

It's not clear if this is possible in your situation, but I would try to similarly run a short 45 to impart at least some amount of immediate slope, as I believe that was the closest approach to what I wanted to do that I found anyone explicitly endorse. If nobody makes such a piece I imagine you could use an appropriate fernco type coupler to connect the straight outlet pipe to a street elbow or something similar on your waste lines. Sorry I can't give more definitive guidance.
 
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