A regular customer of ours called over the holiday weekend claiming her tenant found a “small wet spot” on the carpet..
We showed up on Tuesday to investigate. From the looks of it, the toilet tank gasket has been leaking for over a month.

The surrounding walls were soaked and that “one foot by six inch” wet spot on the carpet was actually more like 8 feet by 2 feet..

We found plenty mold growing behind the baseboards..
and hidden damage behind suitcases and junk in a closet in the next room.

The lesson to be learned, when your toilet makes that filling noise in the middle of the night or basically, when you have not used it,
DON’T IGNORE IT!
Ordinarily the water is just leaking from a bad flapper into the bowl, in this case the gasket between the tank and bowl had failed and
was letting water out on to the floor behind the toilet where the walls and baseboard proceeded to soak it all up.