I’m in the planning stage of finishing my basement. When we bought the house, we were told it was set up for a bathroom. There is an obvious spot for a toilet. I’m a little confused about the vanity and shower/tub.

There’s a pipe that starts here:

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It runs to the left for about thirty yards and then comes down to the left of the toilet:

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Is that intended to be the drain for the vanity? I don’t know why else it would run all that way.

I’m a pretty competent DIY’er but I want to make sure I have this right.

Can you step back and get some better photos?

It's part of the venting system. Air needs to flow just as much as water,  other wise it would create suction like your finger on a straw.

@PNFLDS

Here it is from further back. The pipe that goes horizontally to the left leads to the one next to the toilet:

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Here it is by the toilet:

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There is also this in the floor. I thought it was for a shower or tub:
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This is correct.

almost looks like a Radon vent, the way it goes under the slab and connects to what I'm presuming is a sump pump pit.

There’s a separate radon vent system on the other end of the basement.

That looks like a sewage lift pump.  Would need to know more about the overall house.

Sad they used cellcore pipe. That shit should never be used in houses. When we built our house we only used schedule 40 PVC for drains. Zero issues.

That is a sewage lift pump, you can see the check valve on the pipe on the right.
Is there a pipe for the toilet that is capped off and might be covered by a thin layer of concrete?
Normally, that's what is done.  Then you add the flange for the toilet later on.
I've seen some right at the surface, and others just slightly below.

Sump pumps also use check valves. A sump pump wouldn’t be tied into the home drains but a sewage pipe would. Not sure if that’s a drain or vent pipe tied into the home vent stack.

I’m undecided if it’s a sewage pump or a sump pump. I’d want to look into where the pump out pipe ends up at. That will tell the story. Also, knowing more about where the plumbing exits the house and heads to the sewer would be useful. There should be a cleanout outside the house near where the sewage exits the house.

If it drains to the basement and then exits with gravity then that’s not a sewage lift pump. But, if the main house drain exit point is on the main floor, then the basement will need a lift pump to have a basement bathroom.

I’ve built two homes that had a rough in for a bathroom in the basement. In both cases, the drains for the toilet, sink and shower were all capped pipe above concrete.

To me, the pipe running down the wall looks like a vent. I’d expect a drain pipe to be out away from the wall.

If you have a schematic of the basement plumbing, take some measurements and mark where the drains should be. Take hammer and chisels and remove some concrete to see what you find.

My rough-in has capped off pipes for the toilet (usually 12” on center off a wall) and shower as well as a vertical 1-1/2” pipe in a wall that can be tapped into for the vanity.  Toilet pipe is 3”, the shower is 2”.

Is the lift pump near the bathroom location? Hard to get an idea of the overall layout.

How far off the wall is that boxed out concrete section and where is it in relation to other pipes?

It is the vent for the toilet. You can cut a tee in and catch a lav drain. If the drain is more than a a couple feet away you should do something a little different but otherwise, just cut a tee in and run horizontally ~18" either way if needed.

The blockout could be a tub or shower. Hopefully the underground is configured in a manner the one vent is venting it too. Clean out around that pipe. I'd hope to find a cap there and not have to cut a wye in. It'll need a p-trap.