So.. What am I about to do wrong? Full bathroom reno

[SamInSeattle]

Hey everyone - I'm new to posting here but I've been reading for quite awhile, trying to soak in at least an ounce of wisdom.

I'm in the throes of a surprise basement bathroom renovation, and the budget just shrank, so I've become the plumber. All of my plumbing is below a slab, and still connects to the kitchen upstairs.

I'm hoping this crew can take a look at what I've drawn up and help me simplify and avoid any major headaches. My goal's to start cutting up concrete this weekend. My biggest worry is not having enough depth below the slab to maintain drainage slope and fit the horizontal vent. So.. let me know what you think.

A couple specific questions:
1. Where would a guy put an accessible cleanout for the end of the line? LHS of the toilet maybe?
2. Is it legal to put a Fernco (banded, unbanded, etc.) to attach PVC to a galvanized vent above ground? Right now I have no obvious way to tie into the vent on the RHS without it.
3. I'm unsure if that horizontal wet vent is legal. It's possible for me to switch up this configuration to separate dry vents for the toilet and tub/shower, but it's a little more complicated.

More context:
- I'm in Seattle under the UPC
- I've got a dry vent (LHS of window) and a kitchen sink (RHS of window) coming down from the floor above.
- Another existing vent comes from the wall on the near-right side of the isometric drawings.
- All vents and fixture drains are 2". The main horizontal drain is 3".
- I don't know exactly where the existing horizontal drain is that I'll have to tie into, but I think I'll be able to tie in on the bottom left side somewhere.

Thanks,
Sam

 

[SamInSeattle]

Well I've realized at least one glaring error in my drawings - that being my horizontal wet vent for the toilet and the tub would siphon the tub trap. Doh.

Instead, I'll have to roll off my tub trap arm and run that into the alcove tub wall. I'm still doing some reading to try and understand if this new vent would be able to legally wet vent the toilet. I suspect the geometry will always have me violating code a la the toilet being the lowest elevation, or something. Worst case I end up with dry vents everywhere, I suppose.