Our toilet would run for a couple of seconds every half hour or so. We figured that we had a leak so we turned off the water to that toilet. After several hours, and continuing now for more than 24 hours, I have observed that the level in the tank has not gone down. I put some food coloring in the tank to see if I could determine where the leak is. The coloring seems to have disbursed evenly and the toilet water remains clear. Any ideas on what is going on?

Is the little tube between the fill valve and the overflow pipe attached to the top of overflow pipe or is it stuffed down in the overflow?