When a sink, toilet, or tub becomes clogged, first try plunging. Bail out most of the water but leave a couple of inches so the plunger can seal tightly around the drain opening. Seal any openings -- such as the overflow openings of a bathroom sink or a tub -- by firmly pressing a wet rag into the opening. When plunging a double-bowl sink, seal the drain hole of the other bowl. If you have a dishwasher, clamp its drain hose tightly before plunging so you won't force water back into the dishwasher.
If plunging doesn't work try using a hand crank auger, dismantling a trap, or forcing pressurized water into the drain.
If more than one drain is stopped or runs slowly, take more aggressive steps. Auger through an intermediate cleanout or trap. If that doesn't solve the problem, you may need to auger the main drain. Call a professional sewer service or rent a power auger and do it yourself.
With a rented power auger, an hour or two to run it through a main drain
Hand-crank or power auger, adjustable wrench, pipe wrench, perhaps a hammer and chisel
Identifying and opening traps and cleanouts
Clear the area and gather materials for cleanup afterward
Pipe-thread tape, replacement cleanout plug, bucket
The main drain, the line coming from the street to your house, may be clogged by tree roots that have grown into it. (Many old drain lines are made of clay or have permeable joints.) Open the cleanout plug. If you have a metal cleanout plug, you may have to loosen it with a hammer and chisel.
Rent a power auger with several bits to handle various obstructions. Rental staff can advise on which bit to use. Select the bit and attach it with the setscrew provided on the cable end. Position the auger close to the pipe to minimize the length of exposed cable. Make sure cords are not lying in water. Plug in the auger. Wear heavy rubber gloves. Push the cable into the drain until you hit an obstruction. Switch on the auger and use the foot switch to start the cable rotating. Let it run for a while, then turn off the auger and push the cable in farther.