Tub drain tie in question

[NickScott]

Replacing a tub in the master bath,
PVC drain (1990s house)
Currently it has an 1.5" PVC drain running through the center of the joists for 4' before dumping into a 2" waste line via a wye/45 combo on it's side.
This 2" travels 3 feet to the 3" stack at the toilet.
The other end of this 2" line travels 6 feet to the double bowl vanity and also is the drain line for the vanity, then up the wall and through the roof as a 2" vent.

There is another 2" line coming from this 3" stack, servicing the walk in shower, this has its own 2" vent in the shower side wall.
This line also services hall bath on the other side of the wall.

Questions:
Is the current tub drain line "permissible" being vent via the double bowl vanity drain line?

If I choose, could that tub be drained in the 2" line that is currently draining the shower and hall bath ? (this would put the master tub drain 12" from the showers 2" vent)

NOTE: the toilet is the top of 3" stack,, the 3" line does not go up through the roof as a vent,, appears the toilet is vented via the two 2" vents (vanity and shower/hall tub)

Thanks,
Nick

 

[wwhitney]

1) Yes, if the total fall from the tub trap to the crotch of the 2x2x1-1/2 wye is no more that one trap diameter, or 1-1/2". The 2" line carrying only two dry vented lavs can act as a wet vent. The distance from the lav and lav vent to the 2x2x1-1/2 wye is immaterial.

2) Yes, if the above total fall criterion would still be met, and if that 2" line is carrying at most 4 DFUs of bathroom fixtures (lav = 1 DFU ; tub = 2 DFU ; shower under 5.7 gpm = 2 DFU). A 2" wet vent is limited to carrying 4 DFUs.

Cheers, Wayne

 

[Sponsor]

 

[NickScott]

Wayne,
Again, thanks for your time and knowledge. (you have answered questions for me before)