The best way to fix an overflowing toilet depends on the severity of the clog. You can fix most overflows with the use of a plunger, but for more serious clogs, it might be necessary to use an auger or to remove the toilet in order to fix the problem.
If the water level is unusually high, do not attempt to stop the overflow by flushing the toilet again. This will only refill the bowl and make the problem worse. If the toilet is overflowing quickly, turn off the water by turning the valve behind the toilet. If you are unable to turn off the water, then open the tank lid, lift the float ball and secure it so that it does not drop to the water. Then turn off the water at the main shutoff.
For a slow toilet overflow, first attempt to clear the blockage with a plunger. Place the plunger over the large hole in the bottom of the bowl and press down slowly. Start to pump firmly but with a slow pace. Gradually increase the speed and intensity of the pumping and then pull the plunger back quickly. Repeat these steps two to three times or as necessary, until the bowl begins to drain.
If the bowl does not clear after plunging, an auger — a variety of plumbing snake with a bent end, enclosed in a protective tube — can be used to clear the clog. Do not use a regular plumbing snake, because it can cause scratches and damage the bowl. Carefully feed the auger coil into the drain. After the auger is in position, slowly turn it clockwise while steadily pushing down until it can no longer be turned. Then turn the auger counterclockwise.
After repeating the turning process once more, slowly remove the auger from the drain. If the drain is not yet clear, use the plunger again. Then reinsert the auger and repeat the turning process.
For a severe overflow where a plunger and auger are ineffective, it will be necessary to remove the toilet and clear the blockage from underneath the bowl. With this method, the water must be shut off. After the toilet has been removed, reach inside the pipe and clear out the blockage manually.
When the blockage has been cleared, reassemble the toilet and turn the water back on. Try a test flush to ensure that the toilet has been reassembled properly and that the overflow has been stopped.