I have a Kohler 1.6 gallon toilet, I just replaced the flapper - but every 20 minutes or so I hear a sort of rushing sound. There are no obvious leaks and I see no air bubbles inside the tank when this sound occurs. It is a 2-peice toilet and a few months ago I had a plumber change the seal on the bottom of the tank at which time a new flush was also installed. I have since replaced the rather flimsy flapper that came with the new flush, I have also used a tank cleaner. But the rushing sound still occurs - and the water level in the tank does not seem to go down.
Does anyone know what might be causing this sound? I am trying to avoid the costs of a plumber for what might be a simple solution.