Before you do anything to clear a clogged drain, you should check the other drains in the house. The clog may be deep in the pipes, or it may be caused by a blocked vent. Once you determine the clog to be confined to a single drain, resist the temptation to break it up with a commercial product that contains sodium hydroxide, or lye. This caustic chemical can harm the pipes and the environment, and you don't need it. You can clear clogs by mechanical means, and if you prefer chemicals, there is an effective, nontoxic option. Some methods will require gloves and eye protection.
Clearing the Clog Mechanically
Plunge the drain before you try anything else. When properly used, a plunger can clear all but the most stubborn clogs. Be sure to use the proper type of plunger -- a sink plunger for sink, bathtub and shower drains and a toilet plunger for toilet drains.
Fill the fixture with about an inch or so of water, closing the drain stopper if necessary. If you're plunging a sink or bathtub, cover the overflow holes with duct tape to concentrate the force of the plunger on the blockage.
Tip the plunger when immersing it to fill the cup with water, fit it completely over the drain opening and pump several times. Repeat until water starts to drain.
Remove and clean the P-trap from a clogged sink drain if you don't have any luck with a plunger. Use a snake to clear the drain beyond the trap. If you can't access the P-trap, insert the snake in the drain opening. Use a toilet auger to clear a clogged toilet and a sink auger for any other drain.
A Natural Chemical Drain Cleaner
Pour 1/2 cup of baking soda down a clogged sink, tub or shower drain. Follow this with 1 cup of vinegar, then close the stopper to confine the fizzing concoction to the pipes. If you're clearing a toilet, turn off the water supply and flush the toilet before pouring the baking soda into the toilet opening. Follow this with at least 2 quarts of vinegar. Pour it quickly to create a flush, which will suck the cleaner into the waste pipe.
Let the cleaner work for five to 10 minutes, then pour boiling water into the drain. One or 2 quarts are enough for a sink, tub or shower drain, but if you're clearing a toilet, pour at least 2 gallons quickly enough to initiate a flush.
Repeat the procedure if your drain isn't clear.