Is this an acceptable drain layout?

[jscully3152]

Upstairs master bath remodel
Main drain is 3 inches
3 inch pipe main drain to toilet
2 inch branching off for shower
1.5 inch for tub
2 inch vents going up the wall tapping into vent through roof

 

[havasu]

Why not a 4" main?

 

[jscully3152]

Why not a 4" main?

That be a question for the builders of the house in 1990

 

[MicEd69]

You need to show the dimensions, the fittings you plan to use, and how each of the drains and vent will enter the adjoining pipes. Also, what code are you under?

 

[GReynolds929]

You can't tie fixture trap arms together before their vents. And that is not wet vented if thats what you're going for. This needs to be reconfigured. MicEd has some good pointers.

 

[jscully3152]

You need to show the dimensions, the fittings you plan to use, and how each of the drains and vent will enter the adjoining pipes. Also, what code are you under?

3 inch main connected to 3x3x2 wye, 2 inch pipe going up the wall connected to vented in roof. 3 inch continuing to another 3x3x2 wye with 2 inch branch for shower and tub drain. 3 inch to 4x3 closet bend for toilet.
2 inch shower/tub branch hits 2 inch wye with 2 inch going straight up through wall connected to roof vent. Branch continues to where the a 2x1.5 inch wye splits the shower and tub drain and p-trap. Under the IPC code in my area.

 

[jscully3152]

3 inch main connected to 3x3x2 wye, 2 inch pipe going up the wall connected to vented in roof. 3 inch continuing to another 3x3x2 wye with 2 inch branch for shower and tub drain. 3 inch to 4x3 closet bend for toilet.
2 inch shower/tub branch hits 2 inch wye with 2 inch going straight up through wall connected to roof vent. Branch continues to where the a 2x1.5 inch wye splits the shower and tub drain and p-trap. Under the IPC code in my area.

Also, the vent for the shower/tub branch is 4 feet away from the drains

 

[havasu]

For our professionals to help you properly, we need something similar to the image here:

 

[MicEd69]

Also, the vent for the shower/tub branch is 4 feet away from the drains

The shower drain is closer to the vent you show than the tub drain is, so I'm not sure what the 4-foot dimension is. But as GReynolds929 said, that configuration does not properly vent the tub.

 

[jscully3152]

Hope this is enough info