IPC, any problems with this arrangement?

[Greenmountain]

The 3" c/o is somewhat obstructed but it's also redundant.
The 2" going up is a dry vent, the trap is from a tub, and the 3" combo from a w/c.
Does the 2" vented tub drain count as a horiz wet vent for the w/c here?

 

[John Gayewski]

The 2" is horizontally wet venting the water closet, but it should be 3"up to the trap arm since it's also vertically wet venting the toilet. That's a UPC requirement. IPC doesn't think it needs to be bigger.

 

[Sponsor]

 

[Greenmountain]

I am IPC here, and the 2" will def help in terms of fitting w/in framing...
In real life, could it happen that if toilet was flushed while tub was draining, the toilet trap could potentially be pulled enough to gap it?

 

[John Gayewski]

I think you'd be better off draining the toilet horizontally into the branch instead of from above.

 

[Greenmountain]

I think you'd be better off draining the toilet horizontally into the branch instead of from above.

not sure I follow... that combo would connect straight up to the toilet flange, so the branch is located by the toilet flange.
The arrangement in the pic is not exactly to scale but pretty close.
Would it be better to have the 3x2x3 wye below rather than upstream of w/c combo?
If so, I could increase to 3" below the 2" SanT, bring it out farther (toward viewer in the pic) and back to the 3" branch downstream of combo (in which case the the 3x2x3 would be a 3x3x3)?

 

[Greenmountain]

I was thinking this way might be better as tub draining helps wash toilet debris down the line,
but seems there may also be a slight potential to pull a gap in the toilet trap?

 

[wwhitney]

A simpler version of your initial picture is below (where the fittings are drawn in perspective over the photo, with the white squares indicating the edges of the fittings, and blue is 2", red is 3"). It uses an upright 3" combo (side entry is vertical).

What John suggested is the second version, where there is a 3" wye that is horizontal (side entry has 2% slope) and a closet bend under the WC.

Either way, a cleanout at the upstream end of the 3", and a horizontal 3x3x2 wye.

Cheers, Wayne

 

[John Gayewski]

Wayne's second drawing is what I'd do.