New toilet drain question

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plumbconfused

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Hello all:
I'm adding a new bathroom in an old house second floor. So far have a new 3" drain installed all the way to the ceiling in the room below. I have the subfloor removed in the second floor remodel area and can see my new 3" 90 poking up through the ceiling below (encased in a nice new soffit in the first floor room so it can run a few feet (1/4" per ft descending) before turning through the wall and working its way to the basement).

The floor in the new bath has 2x8 joists. I set it up so the 3" pipe turns up through the ceiling below right where the toilet will sit. The question is, can I put a sanitary T between the 3" 90 and the toilet flange in order to pick up the 2" shower drain coming from a few feet away? I hope this is described clearly

Any help would be greatly appreciated!

Bob from Michigan.
 

Jadnashua

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As long as each of the fixtures are vented separately, you should be able to tap into that drain for the shower. I was waiting for one of the pros to give you the details. The vents can be combined above the flood plane of the highest thing draining into that pipe - typically, that would be around 42" if there is a sink involved, but could be lower if it is only the shower and toilet. The rule is 6" above where it could flood to (the flood plane), and that would be the top of the rim on the toilet or above the curb on the shower, with the toilet being the higher one, it would prevail.
 

plumbconfused

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This 3" drain only handles the toilet and the shower - I have another 2" drain pipe already installed on the other side of the room and running to the basement so it won't have to cut through 10 2x8 floor joists.
So, back to the 3 x 3 x 2 sanitary T vertically placed under the 3" flange in order to bring the 2" shower drain into the drain system: A retired master plumber I have become acquainted with likes the idea of a 2x2x2 Y in the 2" line on the way to the shower turning up and going to a mechanical vent in the wall to vent the toilet and shower. He says it's code and it will work, based on a slightly different routing described below (Y in the 3" to pick up the shower, but still using the mech. vent branching off from the 2" shower drain - details below!).
The whole 3" line goes to the basement and ties into a 4" line that has a 4" stack going all the way back up and out the roof.
He was out of town when I thought about doing the sanitary T under the flange to pick up the shower. I actually already have a Y in the 3" horizontal section under the floor (and it pokes up into the new room through a hole in the ceiling) a couple of feet away, and had planned that for the shower. The good thing about running the shower drain over to where the toilet is, is I cut the 2" hole in the 2x8 joist much closer to the wall and away from the new ceramic tile shower. If I have to cut the hole to run the shower drain through the joist right under the shower, it will really weaken that floor joist and also be dead center in the 10' span of the joist - not good from what I've read. My whole reason for re-routing the shower drain pipe to the toilet is to avoid cutting the joist in the center of its span.
Thinking while typing... I guess I could run the 2" shower drain 5' over to the edge of the room then 90 through the joist then 90 again to go back 5' to go down in the Y that is already installed in the 3" drain below... I'd be running it right past that 3" toilet drain though...
This new bathroom truly was my wife's idea, not mine, and she is convinced that I know what I'm doing.


I'm looking for opinions, ideas, brilliant solutions, etc. before I start gluing PVC and installing 3/4" plywood!
 

Jadnashua

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All of the devices need to be vented...and if you put an AAV in the wall, you must put a removeable panel there to be able to service it. If there's attic above this, it is much better to do an atmospheric vent.

Hopefully, on of the pros will check this out for you. You can make a connection to the 3" for the shower, BUT, as mentioned, the shower needs to be vented first.
 

plumbconfused

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I sure don't understand all I know about these vents and drains. Now that the floor is open and I have access to all the PVC and haven't even glued any pipes in the PVC spaces or even built the shower walls, now is definitely the time to make changes if I need to.
Did all of my description of my planned shower and toilet make sense? Is it all going to work? I am starting to second guess my plumber buddy with his recommendation of an AAV in the wall. Maybe I should at least run it up into the attic?
 

Jadnashua

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AAV's eventually fail...you must have access to it to replace it, thus the access panel.

A normal atmospheric vent that goes through the roof is best. I'm assuming you have at least one vent that goes through the roof. If you have access to the attic, you can combine all of the vents and then use the existing vent. There are size requirements, and you need to calculate how many fixture units there are to determine what size the vent needs to be going out through the roof.

So, what would be best is to vent the toilet up into the attic, AND the toilet. You can then combine them, maybe with the vent from the vanity sink, and then to the existing vent that goes through the roof. Or, you could make a new penetration through the roof with a new vent.
 

hj

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drain

You can't use a sanitary tee if the job is going to be inspected. The vent can come off the shower line in most cases, but the actual way you do it would determine whether it is proper or not.
 
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