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.
Best Answer
I had a similar problem once but the leak was visible and the outside of the toilet bowl was wet. Flushing from the tank produced leakage but flushing with a bucket did not.
It sounds like clean flush water is somehow escaping on its way from the flush valve to the toilet bowl. This could be from a misaligned tank fitting or a crack in the ceramic material. I assume that you have found no water running down the outside of the fixture.
Depending on the design of the toilet, the connection between the tank and bowl parts may include a metal fitting set into the bowl. This can become loose or cracked and thus leak water outside the flush pipe but still inside the toilet.
Or an imperfection or crack in the ceramic could allow clean water to escape from the rim passage or wash passage, well, whatever it's called and the design of these passages varies a lot. The point is, flush water can escape its proper path and still not get outside the toilet where you would see it.
EDIT: couple of pictures to show what I mean:
The red callouts show where an invisible leak might occur only when tank flushing and not when bucket flushing.