Old Church to Residential Reno - Basement plumbing

This is the bathroom of the church we bought. We're converting it to a home. It had a men's room and a lady's room with lots of wood paneling

The photo on the left is what I have. The drawing on the right is what I'm thinking of doing. Basically that drawing can be superimposed on the photo. Is this code worthy? Is there anything I'm not seeing?

It would be the size of pipe indicated, with single and double Y-fittings and 45 degree elbows for the most part. Whatever will give a smooth flow. And the main vent stack will essentially start going vertical about where that toilet flange in the back is.

And then the sink - I read that if water from a large vent passes a smaller vent it may cause aspiration. This is a pretty compact system, so I don't know... Run it back to the tub/shower vent in red ink or not?

Hope that makes sense.

Thanks,
Aaron

WHAT you show is okay. HOW you actually install the rest of the piping will determine whether it is proper or not. It depends on how MUCH water from the upper drain, (not a vent), is flowing past the smaller one, (and how the smaller one is installed), which determines whether aspiration could occur.

In Washington State we're not allowed to wet vent a second story over a lower story.
It has to be a bathroom set on the same floor.

This is Canada, so it's likely different.
I would not have been allowed to plumb it the way yours was.

Thanks hj. Good to know I'm on the right track. Terry, what do you mean by that? The kitchen would have it's own dry vent going through the wall right behind the sink. It's about 40 feet away, so it seems like that would be necessary. I was picturing the kitchen as a separate system in a way, that ties in to the main drain at the end.

Here, the bath group can be wet vented through the lavatory vent, but all others traps require their own vent. A vertical stack is a vent only above the highest fixture drain connection.

Update

I took out the old pipes and dug down to give myself space to work when installing the new pipes. Pretty loamy soil for the most part, but some clay. Also some of the hardest packed soil I've ever dug out. Good times

The tub will go in the back corner, with the drain in the trench behind that retaining wall.

The pipe on the right goes through the wall to what used to be the kitchen. It will become the laundry area, with the kitchen being upstairs now.

The toilet will be in the bottom right corner, and the sink will be opposite the toilet on top of the 4" drain.

So far so good