Why does my toilet lose water -- ITS NOT THE FLUSH/FLAPPER VALVE!?

Question

I assumed the reason my toilet kept losing water because the flapper/flush valve in the tank was not completely sealing the hole (maybe because of the chain or a worn down flap). I was wrong. How it works is when i flush the toilet you hear the Filler valve fill the tank with water and when its done so it stop running. But when you look into the bowl you see little amounts of trickling water pouring from the rim into the bowl slowly. When the tank empties enough into bowl the filler valve makes the refill sound to refill tank and this happens over and over again every 45 mins.

*** Interestingly the water will stop running (and consequently prevent it from losing water ENTITRELY) if i pull up the little tube that overhangs into the Overflow tube. When i pull this little tube out of the Overflow tube i hear a gurggling sound within the little tube... and moments later the bowl stops receiving water via the rim. Problem solved. But why?!?

my hypothesis is that somehow the filler valve when it begins filling the tank (via its open vents at bottom of this valve) and the bowl (via the overflow tube) somehow its tiny tube laying inside the overflow tube is acting as a drain through the filler valve's vent (which sits in the tank)...maybe thru laws of physics water is being pulled up and over into overflow tube via the filler valve's vent

Answer 1

That little tube should be "aimed" into the overflow tube, but not down inside it. They normally come with a metal clip that holds them above the overflow.

Answer 2

I had this same problem. The filler tube(the little hose that goes from the water valve into the overflow tube) was pushed down to far. This created a siphon and would drain the water down until the valve came back on. This happened over and over again. The solution was to raise the end of the hose above the water line when the tank was full. Problem solved.
( P.S. Some water valves come with a little plastic elbow that clips to the overflow tube. You might "rig" one out of an aquarium air tube fitting )

Answer 3

Toilet Tank Losing Water

Answer 4

You just answered your own question. The overflow pipe needs adjustment. It's not complicated like brain surgery.