When your toilet fills up instead of flushing when you press the toilet's handle, a complete clog resides in the toilet's drain line. The clog is not allowing the water to drain out of the toilet's bowl through the drain, meaning after you flush the toilet the extra water from the tank causes the water level in the bowl to rise. Removing the clog through one of several methods will allow the water to escape the toilet bowl.
Close the toilet's fill valve by turning the handle clockwise as far as possible with your hands. This will prevent the toilet from overflowing before you clear the clog.
Pour 1/2 cup of baking soda into the toilet bowl's drain and wait five minutes for it to settle around the clog. Pour 1/2 cup of vinegar down the toilet's drain, creating a fizzing reaction that helps break up the clog.
Press a toilet plunger's cup over the drain opening in the bowl. Pump the plunger's handle up and down vigorously at least two dozen times. The pumping of the auger's handle increases the pressure in the toilet's drain line, which may dislodge the clog.
Push a toilet auger's flexible line down the toilet's drain. Once you feel the auger contact the clog, turn the crank on the auger's housing clockwise as you push the auger through the clog.
Turn the auger's crank counterclockwise as you pull the auger's line from the toilet's drain. Run the auger's line down the toilet's drain up to three times total to eliminate especially stubborn clogs.