Vent fitting for toilet and shower from opposite sides

[Anthony Curtas]

In our remodel, we want to move the toilet to the other side of the room. Route to the main 3" stack is in the same joist bay, so I thought this would be easy, right?

The existing layout has dual lavs running past a tub (each with their own vents), then joining up with the shower drain, which then all joins the 3" existing toilet pipe, which join the stack on a sanitary tee pointed to the toilet along the joist direction. The 3" stack continues up to the attic to serve as the toilet and shower vent.

I want to split that and have the toilet from the other side of the joist bay and the others join it at the same fitting at the stack.

The plumbing store showed me a 3" sanitary cross that looked like it just let toilet discharge flow right to the shower (gross). So I started looking into other options.

Would a 3" fixture tee work? Any unforseen problems other than it needs a bit more height to make all the connections?

I also have seen a 3" sanitary tee with 2" side inlet. I could probably make that work with the shower and tub line and the 3" side would be only for the toilet. But I have no experience with these and just started reading about them (doesn't help that they are called different things everywhere).

Advice here appreciated. Thanks,
Anthony

 

[Terry]

The double santee isn't legal for that purpose.
The double fixture fitting would be better, though even that skips across the fitting with a new toilet using a 3" flush valve.
You may want to consider having seperate fittings, one for the toilet, and one for the shower. You don't want the toilet burping water out of the shower drain.

 

[Sponsor]

 

[Anthony Curtas]

I'm trying to think how I can do that. I've only got 9.25" of joist space there and half of that is eaten up by the drop from the lav coming across the width of the room (9' across so 2" drop and 2" pipe doesn't give me a lot of room to go farther down). I think I see some sketchup modeling in my future. Up is fine, I can vent any of the fixtures differently (add one for toilet or shower)

I'm assuming the side inlet / cottage isn't good for this either?

Thanks.

edit: 9.25" in the josit bay

 

[Terry]

Maybe the side inlet works for you. That means you need to add a 90 there.
Most of the time, I would be going farther down the wall though.

 

[Anthony Curtas]

Like a lot of remodels that's finished space so we're trying to not blow that up. If it has to happen, it has to happen.

I may be able to run a 2" or 3" drain down to the basement and tie into the 3" there. That wall is double 2x4 and non-load bearing. The wildcard there is fireblocking. If there is none I could probably line both up and feed the pipe through.

Time for some exploratory surgery.

Thanks again.

 

[Anthony Curtas]

Just checked the basement again. Not a lot of room for another drain all the way down. Supplies are the next stud bay over and a lot of electrical the next one after that. I'll see what I can reach in the existing bay once I pull up some subfloor. I did realize I can pull drywall in the basement stairs instead of the main hallway to reach these spaces, so that's a plus. Tough to work all the way up where these fittings will be, but not a finished space yet. I'm getting an idea of what this is going to look like, though.

 

[Anthony Curtas]

Question:
If I added venting to the other fixtures including the toilet closer to the source, could I use a double-wye-combo to replace the single sanitary tee I have now? The upper part of the 3" fitting would not serve as a primary vent to anything and the vents would all joint up in that same wall to the 3" stack and go through the roof. My understanding is that those combo wyes are forbidden with vents because the pipe plugs before the water clears the vent opening creating a siphon. If the vents were elsewhere, that would no longer be the case and the deeper fitting would prevent the toilet "crossover" during flush.

This option seems to work better because it allows all the work in areas I have demo'd (and no work in a finished area). The wet wall is a double 2x4 wall, non load bearing, with plenty of room to work.

Thanks.