Shower Drain In Concrete Slab

I have a unfinished bathroom on a concrete slab. I recently decided it was time to complete it. What i thought was the drain for the shower doesnt seem to be the case. I went to Lowes and Home Debot to ask for some advice and they wasnt much help, so here is my problem. Over in the corner is a 1ft by 1ft plastic cover. I fugured the drain was under it. So i cut a hole in the top to further examine what i would need to attatch to the drain. There is a black 2in pipe running in therethat buts against the slab. the black plastic covering looks like some sort of retainer to either keep the water from getting under the slab or the dirt from falling in. I figured i could cut the pipe back some to allow me to attatch the fitting so i went and started shopping for showers. well all the drains seem to be 12in by 12in for the corner showers. The measurements from the wall for what i believe is the drain pipe is 12in by 24in. So i ask, do i need to cut the concrete and move the drain pipe so its 12in by 12in or is there another way. Maybe this in fact isnt the drain pipe. The shower head and shower handle have already been completed in the wall and are 18in from the one wall. Lowes/Home depot seem to believe it was maybe for a garden tub or a jacuzzi tub neither of which will fit since my washer and dryer are on the other wall. Lowes/Home Depot also said since the shower head and handle are already in the wall maybe the last home owner started the project and then came to the drain issue and then stopped. I will try and attach a couple of pictures so you can see what i am talking about. I would draw it out but i am not much of a drawer and well my 2yr old likes to draw on the paper when dad is and i know no one would be able to make it out then. thanks for any help i can get.


Bill
OSC (SW/AW) Mcalister
USN

Another Picture

Hopefully the Pictures will give a better idea of what I am talking about.

Another Picture

Not sure if the last one came out.

Okay Last Picture

Here is the last Picture. I can take more if needed.

If that was intended to be a shower drain, it would likely be capped, rather than running through past that area. Are all of the drain lines in the house abs (black like the one in the pic)?

Could that be the drain from something else?

Yeah I guess it could be but I am not sure what. The toilet drain is in fact capped and when you first walk in on the left the plumming and pipping for a vanity is already there.


Bill

Jim,
I tried looking at the rest of the pipping in the house and the only place that is visable is in the bathroom that i posted the pics of. All the pipping in there is the abs pipping.


Bill

Normally (from my limited experience) a rough-in for a shower or tub will have the pipe terminate in maybe a 12" square open area in the slab. They leave that much room (or more) so that there is room to work when installing the trap, which needs to line up exactly with the new tub or shower. The pipe shown runs through that area, so I don't have an idea what is is for.