We noticed water dripping down the wall below the toilet on the 2nd floor. I assumed it was a leak in the wax ring, especially because the toilet had become slightly loose and rocked slightly when sat on. So I pulled the toilet and replaced the wax ring and secured the toilet down tightly. It still leaked after being flushed. I then replaced the wax ring with a "Sani-seal" silicon toilet gasket. It still leaked after being flushed. So I tried reseating the toilet on the silicon gasket again, with the same result.
I then feared that the cast-iron closet bend had a crack or hole in it, because it does look corroded inside, and does have an indentation that I can see that could possibly let water through. I can't see or access the outside of the closet bend without tearing up the floor or the ceiling below it.
The curious thing is that when I pour a bucket of water straight down the pipe, I see no leakage. Similarly, when I reinstall the toilet and bucket-flush it (with a big bucket of water, pouring quickly), it still doesn't leak. It only leaks when I flush the toilet normally. It doesn't seem like it has anything to do with the supply line - just to be sure, I turned on the disconnected toilet supply line and filled up a bucket, and that did not produce a leak.
My question is, where would this leak be coming from if it only happens when I flush the toilet normally, but not when I bucket-flush it? Could it be that there is a hole in the closet bend that the water only reaches when it has the right type of momentum from being flushed?
Thanks for reading.