relocating toilet and shower (tub) drain

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GatorKenD

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Hi all - hopefully starting a new thread is the right protocol here. Short history: I posted a question April 2013 about switching the location of a toilet and shower that are on a concrete slab (https://terrylove.com/forums/index.php?threads/relocating-toilet-shower-on-concrete-slab.51279/). Short version I didn't have enough info for you to work off of. Then, somewhat unrelated, I had an inspection problem on a home addition I'm doing when the the plumber tried to put a washing machine drain upstream of two bathrooms wet vented together (https://terrylove.com/forums/index.php?threads/failed-inspection-advice.58234/). The result of that second post leaves me believing I can come back to the table with a lot more info. First picture is the architect's drawing of the current arrangement (which, as HJ suggested last year, bore no resemblance to the actual work):
architects plan.JPG

Second picture is how I believe the bathroom is currently plumbed:
plumbing plan.JPG

Third picture is my attempt at a 3D picture of the same thing (how I believe the bathrooms are currently plumbed):
bathroom plumbing.JPG
Things I KNOW that lend credence to this are: the location of the cleanout, the location of the vent stack and the existence of a horizontal vent inside the wall from the lavatory toward the main vent stack. Fourth picture is what I want the new layout to look like.
bathroom g.JPG

My question comes down to picture five: Can I cut out the concrete slab (indicated by red dashed line), reverse the positions of the toilet and tub drain, but still tying them back in to the original pipes that branched off the main drain? In other words, extend the drains as indicated in red. The toilet drain and the shower drain are currently about 34" apart.
re-plumbing plan.JPG

{phew} and thanks!
 
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hj

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IF it is the way you show it, then neither the tub or shower are vented and they are improperly connected to the main line. There is a good possibility that the shower is connected to the vertical line between the two toilets and if so, you would be making a HUGE "U" turn to do what you want, and in the process install the trap too far from its vent. The toilet would work the way you show it.
 

GatorKenD

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Argh... clearly I don't understand wet venting. I thought from the drawings Terry uploaded (on my post about the washing machine upstream of the wet vented bathrooms) that I could have a situation where the portion of the main drain (in red, below) would be the "wet" portion of the wet venting.

Maybe I should reword my question to simply, "HELP?!"

The things I've observed and know to be true I've marked in light blue.
1) I know where the fixtures are.
2) I know from where the vent stack penetrates the roof that it runs inside the wall between the two baths and, if it penetrates the slab in about the same place as the roof, is either centered between the toilets or slightly upstream (toward the clean out).
3) I know the cleanout is centered squarely between the walls separating the two baths.
4) I know that behind the lavatory trap (and inside the wall between the two bathrooms) the trap arm connects to a vertical pipe that goes straight down into the slab and up a short distance before it makes a 90-degree turn and runs toward the vent stack.

This house was build in 1979. The architect/builder built it for himself and there's nothing about this house the would suggest to me that this would be one area where something wasn't code. That is to say, if what I've drawn elicits a response of, "that's not to code," then the mistake is probably in my drawing. Given how many "knowns" there are about this situation, I'm guessing there aren't too many different ways this would have been plumbed together if the plumber wasn't going out of his way to make his life hard.

How would you suggest I proceed. I'm ok tearing more holes in the walls if looking for detail on vent stacks would be helpful. What doesn't seem like a good option is cutting "exploratory" holes in the concrete slab. Also, if my assumption that the main drain runs directly under the wall between the two bathrooms, having to take out walls AND cut the slab under them to access the main drain seems impractical. Just to reiterate: I don't want to move the toilet and shower too far... 38" would be about it.
bathroom plumbing2.JPG
 
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hj

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Unfortunately, NO plumber would have installed the piping the way you show it in this picture. IF it were done that way then NOTHING, except the lavatory, is correct, and the "main vent" is strictly cosmetic and does absolutely NOTHING as far as venting goes. There are MANY ways different plumbers can do the same job with out making life difficult for themselves. I would have installed the main vent between the two toilets.The toilets AND the shower would have connected to it with a single fitting. The sink and tub would have connected to the vertical vent between them. NOTHING, other than those two vents would have connected to the "main horizontal line". But, there are other ways it could also be done, so "guessing" about what is buried under the floor is a useless task.
 

GatorKenD

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HJ - If the shower and toilets are vented the way you describe, that puts the shower trap at about 36" from the vent right now. If I moved the shower trap to where the toilet is (turning that drain into a "U"), that would put the trap 72" from the vent. Is that too far? How far can the trap be from the vent?
 

hj

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It is not only too far, but it makes a very "poor" installation, and also "violates" the "maximum of 135 degrees of turns between the trap and the vent" rule.
 

JohnfrWhipple

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I can remember on one job way back the plumber had to loop the waste line. It was a good 180 degree turn on that job. I think that was the only one we have built that had more than 135 degrees like HJ recommends.

The Ptraps are movable and twistable. So if you gain the 55 degrees from the PTrap then use up the 135 degrees from the other fittings down stream is this still not OK.

It's possible to get nearly 170 degrees turn from the P Trap on itself.

Am I missing something here?
 

GatorKenD

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If I put the tub at the other end of the bathroom, I can avoid the U-turn entirely, but that's a little further. That would make the distance from trap to vent 89". Too far?
 
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