I am considering putting a bathroom in the basement. When we built the house we payed to have the rough in done for a half bath. One thing I realized later on is they put this in the worst possible location as there is duct work right above where the toilet is. Anyhow I am just trying to understand which pipe is for what. I know the toilet flange is the 4 inch. I believe the one next to that is for venting, and the other is for the lavatory. My trouble is trying to understand how to do the venting. I have attached a picture of where I believe the vent from the master bathroom vents. The other picture is from the waste of the kitchen sink, I don’t see anywhere that vents. Do I run a horizontal pipe from the lavatory pipe to the vent and then the vent straight up and tie into the same vent as the master bathroom? Any advise is appreciated.

 

If this helps, I took off the tops and looked into the 2 inch pipes. The one on the right has water in the bottom and the middle one does not. I am assuming that is a p trap, but if that is for a vanity, wouldn’t the p trap be done inside the vanity itself?

 

The 2" pipe with water in it has a trap and therefore is for the shower. The other 2" pipe is intended for the vanity, probably continuing up to the ceiling to vent out the roof.

What is the 2" pipe from floor-to-ceiling with the cleanout? Is that a kitchen above?

The master bath that you have up one floor. I see the 3" toilet. Then the 3" tees off over the steel I beam somewhere - and also converts into 2" and 45's up into the wall. That 2" could be a possible vent - but could also be the master bath vanity. Can you confirm that?

 

We only paid to have them rough out for a half bath, confirming by the sales order. Was only supposed to be toilet and vanity. So if that’s for a shower, then it has to be a mistake. I measured center 2 center on 4 inch pipe to the right pipe and it’s 30 inches, which makes sense for a vanity. The middle pipe is far to close for anything. Also if you see in the first picture, the 2 inch pipes are not lined up to be inside the same wall, so that doesn’t make sense.

yes the pipe with clean out is coming from the kitchen, just wanted to show what was close and don’t understand why no vents.

the 2 inch that 45s has to be a vent, the vanity is to the left (not pictured)

 

Ok, now you have me stumped. I see how the two pipes are too close for a vanity and shower. They are also not aligned, which would support a stud wall. The right pipe shouldn't have water at the bottom, as there shouldn't be a trap there. Possibly the pipe shifted as they were pouring the slab and it dropped? maybe?

Maybe one of the others here will have a better idea.