My next door neighbor found a crack inside the tank of her second floor toilet that ran the entire length where the floor of the tank meets the back wall, and partially up the right side.
She made the right decision and replaced the toilet.
We advised everyone in our annual condo association meeting to inspect the insides of their tanks, especially those people who had the original toilets installed in 1986.
If that tank had broken, there would have been major damage in my neighbor's unit, as well as in mine as that toilet is on the other side of the wall where my computer room is.
I have seen what a major leak can do. In 1985, I was living in a new 3 unit apartment building. The washers were on the second floor. I had one end unit. My washer was brand new and professionally installed. The tenant in the opposite end unit installed a used washer with used hoses. She left with the water turned on, a hose burst, and the entire building got flooded; my first floor having at least an inch of water in it. Then, when I arrived home to find all my furniture out on the lawn, the tenant whose machine had caused the flood was out on the lawn sipping on a glass of wine and tee-heeing that it was "just one of those things"!!!
I would rather spend money on a new toilet and correct installation of water using equipment than risk a flood!
achutch, nice and dry in Vermont