There is one other potential water waster. It could be a leak or an adjustment problem. If the water is running into the overflow tube, it will continue to do so until you do something about it. The ball cock is the valve on the left side of the tank which refills the tank after a flush. There are many different styles of this valve. Like any other valve, it can leak. Since it is easier to readjust it than fix, let's start there. Try to adjust the ball cock or the float to lower the water level to 1/2 to 1 inch below the top of the over flow tube.

Some ball cocks have adjustment knobs on them. Most are adjusted by moving the float, in this case, down. If yours is the type with the float over on the right of the tank, the adjustment is made by bending the rod. To do so, hold the rod steady with your right hand and, with your left hand, bend the float end of the rod down a little. Flush the commode and see where the water level ends up. Re-adjustment may be necessary. If the valve continues to leak, some can be fixed by replacing a diaphragm or several washers, some are best pitched and replaced. Be sure to buy a valve that will not siphon tank water back into the city water system.