Back to back restroom under slab drainage

[fathom73]

I'm working with larger drain pipes under a slab and want to keep everything as simple as possible while having a bunch of fixtures. Attached is a drawing using a sweeping wye for each fixture. The fixtures are directly above the main branch and I'd like to sweep directly into the top of the main branch. What are the main violations for this design? How would you do it? Thanks in advance for any advice!

 

[hj]

The way you have it drawn, almost NOTHING is vented. and the vents you do have are incorrect. You also do not have traps on the underfloor drain lines.

 

[Sponsor]

 

[fathom73]

The way you have it drawn, almost NOTHING is vented. and the vents you do have are incorrect. You also do not have traps on the underfloor drain lines.

I was looking to use the bell traps which would be a foot above the sweeping wye for the floor drains; I didn't draw those in. So the large 4" stack between the toilets won't allow enough venting when wet venting the sinks to it? I'm trying to figure the best way to do this with a single trench using only two 2x6 walls at the beginning of the run and between the two toilets. Is it even possible?