No plumbing decline in apartment building

[Thierry Van Roy]

So I've been looking at this aborted construction project and there are a million things wrong with it. One thing my initial inspections came up with and really bugged me was an exposed pipe which had NO decline (it might even be defying gravity).

Yes, whoever did this turned it into a disaster and yes, the contractor is in bankrupcy. So no, I can't hold him liable anymore (can't pluck a chicken with no feathers).

What I don't know is how the other plumbing has been done. Some is under hardwood floors, some is sealed under concrete.

My inspector couldn't get underneath the concrete, so my question:

How can I check the entire plumbing and what would fixing this cost me?

Are there inspectors who use X-rays or something to make sure? Suppose I wouldn't have to go through concrete (the hard floors need to go, different story), Is there an easy fix or will this be a total redo?

What am I getting myself into here?

Would love to hear anyone's thoughts, because this decline thing is new to me, especially in this large a project (18 large units, 5 floors).