In my toilet, when the shut off water valve is open:
Water leaks above the coupling nut:
If I close the supply water valve and the tank is full, there is no leakage. What could be causing the water leakage? The water supply line is less than a year old. I also taped the connection where the coupling nut screw over and it is still leaking.
Is it possible that the water supply line is broken at the nut? Should I get a new one? The supply line I have has a plastic nut and is flexible.
There was actually a hairline crack in the plastic tube that comes out of the tank to the outside. The plastic pipe was replaced with a brass one to fix the issue.