New house - inherited confusion

Hi all sorry this is my first post but this place seems pretty good to go to.

I bought a new house about 8 months ago with a half finished basement. The bathroom hasn't been done at all but there is some plumbing waiting to be used.

There's a confusing thing going on with the drain in the bathroom and I'm not sure what the intention was.




The drain going to the ceiling is for the kitchen sink. The hole in the ground with the drain pipe coming out of the sill 'inside the wall' is not connected, it's just an 'L' shaped drain that goes thru the sill into the dirt - not connected to the drain.

I have -no- idea why that segment is there within the wall - My -GUESS-, is that the previous owner / plumber wanted to move the kitchen drainpipe to within that wall, and turn the existing hole in the concrete into the tub/shower drain.



My other question lies directly opposite of the drain pipe (this is with my back to the drain pipe pics from above)

Left to right: Toilet rough, ???, Drain for a bathroom sink.
What's the bigger, capped off pipe in the middle for?

Thanks for any help!

My guess is the capped pipe is for the vent and you are correct about the toilet, but guessing is rather pointless when you need factual data. My advice is to hire a plumber to evaluate what you have and give you an estimate for what it will cost to do what you want. There are many places a novice can screw up, and on line advice can only help so much. It really takes someone on site to determine what you have. Plumbing that will be covered with concrete is no place to have to redo. You might be able to do some of the concrete busting and such to save some labor costs.

pipes

We can guess all we want to about all of those pipes, but without knowing how they are connected under the floor we could be completely wrong. The large pipe is the toilet vent, but it could also be a toilet vent AND sink drain, with the other one a vent for a shower/tub drain which has a trap under the concrete. That would be the most common installation.