Another Basement Stub In Question

[Oleo]

I’m sure this gets asked frequently, but I wasn’t able to confidently decipher my basement stub in from previous posts.

1 is a 2” pipe, pretty close to the wall. Guessing this is a sink drain.​

2 is a 4” pipe. I’m guessing toilet on this one.​

3 is a 4” pipe that has a screw cap about 6” below grade (shown in separate picture). Looks to be a back flow valve when I take the cap off. ​

4 is the stack. I don’t have any questions about that.​

My planned bathroom will have a sink near #1, a toilet near #2, and a shower near #3. I’m hoping there is some use for #3 for my shower because it’s pretty close to the correct location. Can I tie a shower drain into the top of the back flow valve, or is that meant to be left accessible for clean outs? If I need to leave it accessible, can I tie a shower drain in upstream or downstream of it?

I also included a picture from original construction, but I’m not sure it helps. The pipes in question are at the bottom-left of that picture.

 

[wwhitney]

Looks like your rough in was only for a half bath, no provisions for installing a trap below the floor for a shower or tub.

No, that backwater valve can't accept drainage from the access cover, and yes, you will need to keep the access cover accessible in the final bathroom configuration.

To add a trap below the floor for a shower or tub, you will need to break concrete and connect the trap arm to the 2" lav drain, or to the WC drain downstream of the lav connection (not between the closet flange and the lav/WC wye)

I guess you could get a tub with an above floor drain outlet and connect to a trap above the slab, with its trap arm connected to a san-tee on the 2" pipe just above the slab. The lav would still connect to that 2" vertical pipe, above the tub san-tee.

Is there a vent stub down in the ceiling above the 2" pipe?

Cheers, Wayne