I purchased a Kohler Portrait toilet within the last year. It now has a continuous leak/refill/leak cycle where it refills itself every 10-15 minutes or so. The water is definitely leaking into the bowl (I checked it with dye). I also turned off the water over night to try to ID where the leak was. Interestingly, the water level in the tank dropped to about half way down the tank then stopped – nowhere near the flapper, and not near any other point where there seemed to be a leakable spot. I then tried again and turned the water off for over a week with the exact same result (water dropped to exact same level). I also tried replacing the flapper (although with a non-genuine kohler part) and it did not help or hurt the situation at all. Any ideas what is causing this and how to fix it?