photoflavor wrote:
Thanks everyone for the replies. We discovered some of the grout
around the toilet is wet, but there is no other visible sign of a leak
on top of the floor. We stopped using that bathroom, and the bubbling
paint in the dining room has subsided. SO, as other's have pointed
out, wherever the leak is, it's due to use - likely a drain
somewhere. I'm not thrilled about the idea of it possibly being
drainage from the toilet!

That would indicate probably the toilet flange seal...

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