Why does my toilet suddenly fill the tank?

SOURCE: Toto Toilet - no water flow to refill tank after flush

Remove the tank lid and look at the fill valve. Is it a yellow valve?
This fill valve is common on the Toto Toilets and can easliy plug with debrie.

They can be disassmbled and cleaned. however, I usually just replace the valve with Fluid Master Fill valve.
You will also want to check the water coming into the toilet by turning off the water that supplies the toilet and disconnecting the water supply line. After removing the water supply line turn on the water at the valve to make sure that the water is flowing properly. Check the supply line also to make sure it is not plugged.
Be sure and place a small container to catch the water that will come from the valve. A towell will also help from making too much of a mess.
If the Supply line and the valve are clear the problem is in the fill valve.
The G-Max system denotes the Flushiing system which is a 3" flapper that allows the water from the tank to flow into the bowl quicker.
Good Toilets!

sanray

SOURCE: Toilet Refills Every 15-Minutes

I have minute amount of leakage into the bowl causing mold to grow. I believe that it may be the rubber seal for the flapper body to the porcelain.

SOURCE: toilet tank will not refill with water after flushing

I fixed the problem. There was a clog in the pipes so i just flushe dthe pipes out.
thanks,
for your help

SOURCE: Toilet tank not filling

shut the water off to the toilet .Remove the toilet supply from the tank end.slowly turn the valve on to see if their is any water coming thru the supply.If water is coming thru the supply than you know you need to change the ballcock.This is the part in the tank where the water comes out of.

SOURCE: When i flush the toilet, the bowl doesn't fill

there is an ajustment on top of float assembly
to adjust level of water in tank