A basement slab could be damp all on its own. Wood can warp in moisture. So, it's hard to say what is the problem or even if the plumbing is the source of moisture you are not sure you have. It could also be a tree root cracked the foundation if it wasn't done well. Lots of reasons.
You might see if you can rent or find someone who has a wood moisture meter and see how damp the wood floor is. Kind of expensive unless you have a need for one long term (i.e., you're a woodworker or maybe a contractor).
Is there any signs of moisture around the base of the toilet or any other fixtures.