What's worse than a water leak ruining your ceiling?

An intermittent leak that's what!

We have had a drip coming through the sheetrock above the basement toilet and below the upstairs tub and toilet for a couple days now. I assumed that if I removed the inspection panel behind the tub controls in the upstairs bathroom that I would find something leaking, maybe a pressure line to the tubs valves dripping.

But no... Everything in there is bone dry. And the drip has started and stopped a half dozen times now. It might drip with enthusiasm for a couple hours and then quit entirely overnight. I can't figure it out.

I'm pretty certain that I am going to have to take the sheetrock saw to the boxed in area where the leak is coming through just so I can get a view up into the rest of the area where the pipes run. But it's not leaking right now so I guess I'll go hook up the boat...