What sizes are the pipes? Can't tell for sure from the pix.

2" required for shower drain.

3" minimum for toilet drain (4" preferable)

The pipe in the ceiling is probably a vent. Does it lead all the way through the roof?

This is a probably rough-in for a basement bathroom.

C, D F, and G are drains. G is for the toilet, although it's a little small. It should be 4", but with the new low-volume flush toilets, it should work. C and D are for a double vanity. F may be for a bidet or it could be for a urinal.

H is probably a vent.

A, B, and E are most likely radon vents, but why they terminate inside the house and not outside is a mystery.

This is all guesswork based on the photos. You should have a plumber look at it.

OK. I do not know if the vent pipe goes all the way through the roof, but I can trace it along the basement ceiling about 12', and then it goes up. I assume that it goes on up between the walls of the 1st and 2nd story.

None of the pipes are for Radon. When we purchased the house under construction, we asked for a Radon mitigation system to be installed. The builder had to cut/dig out the concrete to place the large pipe into the ground. The pipe is on the other side of our basement. It goes out of our roof. The builder told us that these pipes were a rough-in for the wet bar and a bathroom. I just don't know which plumbing fixtures go where.

Measurements: (With pipe caps on top)

Pipes A, B, D, E, and F are measuring 2 ½ "

Pipes C and G are measuring 3 ½ "

Hopes this helps get some answers.

Are these measurements inside or outside diameter? If OD, then

A, B, D, E and F, are 2" drains for sink, tub, shower or bidet.

C and G are 3" drains for toilets and urinals. This is the old size, the new size is 4".

I measured the tops of each pipe. And as mentioned, there is a very thin cap on each of the pipes.

Also, I am positive that there was no plan for a urinal or a bidet. We live in Tennessee. LOL

So if there are 2 - 3" drains, I wonder what the second one is for. Do the heights of drains make a difference in what they are used for? My guess is that G is for a toilet since the vent pipe is located above this. But what the heck is the smaller pipe (F) for that is located just in front?

Did you all forget about a shower and/or tub?

The construction drawings should be on file with your AHJ.

But what the heck is the smaller pipe (F) for that is located just in front?

"Front" is relative. It may be to the side as the architect envisioned the bathroom. I still vote for bidet. Just kidding. I actually have not idea what it might be for.

OK, actually it's behind and to the side. Perhaps I should get a ladder and take a photo from above looking straight down. I'll do that tomorrow evening. We have two house showings earlier tomorrow. That's why I am looking for answers so that I can tell potential buyers about the rough-in.

catbuilder - What do you mean? The shower and tub were mentioned. And I have no idea what an AHJ is. I have some plans, but the basement rough-ins are not listed.

AHJ= Authority Having Jurisdiction. The permit office for your county.

3" is probably a toilet. 2" is probably a shower. Height doesn't matter since you would cut them off when finishing. 2" can also be a sink drain (lavatory or bar sink).

Thank you everyone!

I took a photo from as far above as I could reach with my arms. Can't find the ladder. :)

From the direction that I took the picture, I am standing in what would become a hallway. Click to enlarge.

I would love to have someone draw over this photo what you think might be an approximate layout of the bathroom. I guess there is the possibility that it was plumbed for a bath and a half, but I cannot figure that out.

Also, below is a sketch that I have done of the layout of the basement and where the wet bar and bathroom areas are to be. Please note that none of this is exact!!! Unfinished areas in red.

The small purple circles are approx. where the PVC pipes are located. The long purple and yellow is the vent stack and the line it follows over to an existing wall. Click to enlarge.

There is the possibility that the contractor installed multiple drains so future owners would have some choice about whee to put fixtures. The unused drains would then be capped off. I don't think you are under an obligation to use every drain for some sort of fixture.

Would 'F' be the vent for the toilet drain?

Good point StarCraft!

greg - If G is for the toilet, I have no idea about F. Do toilets have a vent?

All drains need a vent at some point. The vent prevents the traps from getting sucked dry when water is flowing down the drain. It breaks the vacuum.

Maybe 'B' is the vent for 'C' and 'E' is the vent for 'D'

The traps for a shower would be below the concrete and therefore would need a vent that's also embedded in the concrete and connects to the drain after the trap. So C and D might have traps.

The trap for a toilet is in the toilet itself, so there shouldn't be a trap below the concrete. But again, you'd need a vent connected below the concrete which is why I suspect that's what F is.

(Note: I'm not a pro. I just have a rudimentary understanding of plumbing, so hopefully someone more knowledgeable can either confirm what I'm saying or point out where I'm wrong)

I really think you should get a plumber out to confirm what's going on. They can probably stick a camera down each pipe and see how it's all connected up down there.

If B, E, and F are vents then they'll need to be connected up to the vent pipe in the ceiling to complete the venting of the drains to the outside.

Very helpful...thank you so much! :)

Your layout makes sense, now. There will have to be a 2 x 4 or 2 x 6 wall on the outside wall (against the concrete block. Those tallest pipes, being drains, will be hidden in the wall along with water and electrical. Same for the vent next to the tub.