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Every toilet I've ever worked with (not many, I admit) has a stack in the wall directly behind it, including mine. I'm re-doing my bathroom and I'd like to install a wall-hung toilet. I have 2x4 construction, and Toto makes an in-wall tank designed to fit between 2x4s. Great. However, the diagram they give indicates my stack would by right in the way of the tank, and their document doesn't contain the terms "venting" or "stack" anywhere. Here is their installation guide (PDF)

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What do I need to do to make this work?

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Good question. That manual seems to just show the soil pipe going straight down, right underneath the tank, with no vent. Maybe it's worth a call to the manufacturer? I assume you'll have to follow @MichaelKara's advice and move the toilet or the stack (if it's really there). Maybe that style of toilet is really intended for new installation. – Henry Jackson Oct 31 '13 at 4:02
up vote 6 down vote accepted

The simple answer to your dilemma is that you have two choices..either relocate the toilet location to one side of the vent stack - or - to route the vent stack pipe around the place the 'in-wall' components are mounted.

On top of that if your stud spacing is not now 25-3/8" you may be doing some framing work in your wall anyway.

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You are correct, of course. Unfortunately, it is impossible to move a 3" stack across 2x4 studs. I did notice that the tub is sharing the same drain/vent system as the toilet, so I think if I took its drain and vented that (it's only 2"), the whole system would be vented and it would work. Still, it's looking like this might not be the best idea and I might have to revert to a normal toilet. – Greg Smalter Nov 2 '13 at 2:18

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