John, I know that feeling I was in my workshop a few weeks back and water started pooling above the ceiling. I'd been chasing a squealing sound in the pipes for a few weeks and so my wife thinks it's related and asks me to call a plumber.
Well, turns out it was completely unrelated and a quick fix....but then I ask him to chase the squeal. He assumes it was the bladder for the water heater (which was also bad) and changes that. The damn squeal gets worse and we've paid $300~ for the repair.
I continue chasing the squeal and narrow it down to the toilet....now that it's more consistent. So I believe i have it narrowed down to the shut off valve at the toilet since rotating makes the noise happen. I change it.....nothing...still the same noise.
A couple days later I decide to simply replace the internals of the toilet and finally end up fixing the noise since after all that it was actually the toilet fill valve making the noise....
Then, as a bonus I got to replace a good portion of the drywall for the ceiling in the basement... a great way to enjoy the weekend, IMO.