This is happening with both toilets in my house. It also happens when I bump or jar the toilet or turn on another faucet in the house. Every 5 minutes or so, the fill tube lets water into the tank for about 3 seconds, then stops. I have drawn a line in the tank, and the water level doesn't seem to be changing, despite this contant fill. I have also noticed when the fill happens, bubbles flow out of the fill tube, so not sure if it's water or air, but there is definitely a water sound. My sleep is disturbed by this constant sound and I'd love to get it fixed! Any help is much appreciated. Toilet brand is Sterling and the house was built in 2001. Thanks, Christyne