It may be because someone flushed something down the toilet that he shouldn't have or because a clog that had been slowly developing suddenly reached critical mass, but your toilet just stopped draining in the middle of a flush. Don't worry – you can probably clear things with a plunger. The first order of business, however, is to interrupt the flush and get some of the water out of the bowl, or it will end up on the floor.
Do Something -- Quick!
Don't just stand there with a horrified look as you watch the water steadily climbing to the rim of the bowl. Open the tank and push the flapper down – it's the rubber valve cover on the bottom of the tank. That interrupts the flush and sidesteps the unthinkable consequences of an overflow. If it's too late or your toilet has a canister-style flush valve, you'll at least have the satisfaction of having tried.
Drain the Bowl
The easiest way to drain the bowl is simply to avoid using the toilet for an hour or two -- few clogs are complete enough to prevent water from seeping through. If you don't have time, get your rubber gloves, goggles and respirator and scoop water out of the bowl and into a bucket using a tin can or a jar from the trash. Take the water outside and dump it on the lawn – your grass will thank you for it.
Plunge the Clog Away
Plunging clears about 90 percent of clogs, as long as you use a toilet plunger -- which has a flange that fits inside the bowl opening -- and not a semispherical sink plunger. Hold the plunger under the hot water tap in the sink to make it more flexible before using it. Fit the flange inside the toilet opening and pump sharply. After several pumps, remove the plunger and wait for water to drain -- it probably will.
When a plunger won't clear a toilet clog, a snake – more properly called a toilet or closet auger – usually will. Don't use a sink auger – it doesn't have the same reach or clog-clearing power. Feed the head of the auger into the toilet opening and push until it won't go any farther, then crank the auger handle. This makes the head spin, and its blades can cut through debris. When water begins draining, retract the head. Be sure you're wearing your rubber gloves because the head will probably need to be cleaned.