I have some basic home DIY skills, including sweating copper pipes, as my home in VA is prone to pinhole leaks. I have a weird thing that happens about once per year though: Above my kitchen is a bathroom with toilet. Close to where the toilet is, I get a massive leak of water that pours through ceiling into kitchen. I open up the ceiling and let it dry out. I inspect the pipes - there is no longer any leak. I inspect the toilet upstairs and it is securely bolted to the floor. I close up the ceiling, and about a year later it all happens again. Again, unable to find source of leak. Any idea what is happening?

not trying to be gross but does the water smell?
do you see any staining of the underneath of the sub floor where the toilet drain sticks up thru?

Did you open the ceiling directly under the closet bend? The mystery is the once a year thing. As if a giant Rat relieves himself annually... just kidding but it is a puzzle.

No - water doesn't smell bad - I initially I thought it was a leaking pipe.

Yes I could see the closer bend. Since there is no constant leak, I'm assuming it is something to do with the toilet. It is odd - maybe not exactly once a year but it happened recently and last time was prob. About 12- 18 months ago. I may end up just replacing the toilet but I was wondering if anyone had come across this before.

check the refill hose inside the tank. it could be loose and occasionally squirt water up against the tank cover which would dribble down the outside ??