Shower and Toilet Drain Sequence

[quinocampa]

First post! Name's Dan. I'll put it in my sig.
Okay, I have gutted my bathroom completely and will be moving all fixtures. The toilet and shower drains have not yet been done. What would work best for me is to have the 2" shower drain join the 3" toilet drain through a wye or waste tee, downstream of the toilet. The toilet drain is perpendicular to the joists in the crawlspace, while the shower drain would be parallel. They would enter the crawl through the subfloor in adjacent bays. I am concerned whether it is acceptable to have the shower downstream of the toilet. I want the 2" to drain into the 3" from above, rather than in the same plane, but that's contingent upon space.

I'd like the toilet drain to meet the main drain where I cut off the old toilet drain. It is only 2" below the bottom of my joists and the run is about 7 ft, giving me just a bit more than 1/4" slope per foot. The toilet drain will always be below the joists though, because of running perpendicular. That is why I think the shower drain can empty into it from above.

Thank you!

 

[Terry]

And the shower will need to be vented betwee the wye on the 3" line and the p-trap.
The vent must use waste fittings below the flood level of the fixtures.
If you intend the wet vent the shower, then the vent needs to be 2" or more.

 

[Sponsor]

 

[quinocampa]

I follow you -- the shower has to be vented on its own line before it joins the toilet line. This is the tricky part for me, because the drain is running parallel between joists, and I want the drain to be in the middle of the shower floor, away from the walls up through which the vent would run to meet the main 3" vent. I may have to shift my drain on the shower floor over toward one wall.

 

[quinocampa]

Plan View

Here is the plan view of my bathroom. The colors were much more vivid on AutoCAD before I saved it as a jpeg. Anyway, the shower stall is below the toilet in the drawing, and the shower's right wall is the wall behind the toilet. It would be best if I could get the shower vent up there, and a toilet vent also, joining behind the toilet and going up into the attic to join the 3" main vent. You can see though that the shower vent would have to cross joists in the crawlspace to get over to that wall.

 

[quinocampa]

And the shower will need to be vented betwee the wye on the 3" line and the p-trap.
The vent must use waste fittings below the flood level of the fixtures.
If you intend the wet vent the shower, then the vent needs to be 2" or more.

Can I have a vent on the 3" toilet drain line between the toilet and where the shower drain enters the line through the wye? And that vent serving to vent both the toilet and the shower lines both? That would be a form of wet venting, correct? Since that vent is upstream of the shower drain output.