Lye, or sodium hydroxide, is an ingredient in many drain cleaners and it also available in its pure form. While lye is effective in clearing out tough clogs, use it with great caution, as its caustic properties may cause severe or even fatal injuries if it comes into contact with bare skin, is inhaled or ingested.
Lye, also called caustic soda, is available as powdered crystals or in liquid form and can eat through most surfaces it comes into contact with. Even as an ingredient in drain cleaner, its corrosive action works its way through tough drain clogs composed of accumulated hair, soap scum, paper products and grease. The severity of the clog determines how long the lye must sit in the drain as it works. Use great caution at this point to prevent injury.
Before using pure lye, or any drain cleaner that contains lye, it's important to read all the instructions enclosed in the packaging and to put on protective gear that includes eye covering and thick rubber gloves. As lye can also give off toxic fumes, it's a good idea to wear a respirator or a mask, particularly if dealing with a tough clog or an open floor drain. Never touch the lye directly with bare hands and don't inhale any fumes produced by mixing the lye powder with water. Pay close attention to all aspects of the job and go outside if you suspect that you've inhaled lye fumes. Never mix lye drain cleaner with other chemicals and store it safely away from children and pets.
In the event of skin contact with lye, wash the burn with lots of water and don't rub the area, as its caustic effects can be spread to other parts of your body. Get out of the affected clothing and don't touch children or pets. For contact with eyes, flush them right away with water for at least 15 minutes and contact a physician if the irritation persists. If you've ingested lye, drink large amounts of water or milk but do not induce vomiting, as the lye's caustic action can damage the esophagus. Get to a poison control center immediately.
For most clogs, pour the lye cleaner directly into the drain. Use only the amount recommended in the instructions and allow it to work for the prescribed amount of time. Rinse the drain well several times to be sure that none remains in the pipes. Using more than the recommended amount of lye drain cleaner creates a higher concentration that can result in damage to pipes and be harmful to the environment. If you're not sure whether your plumbing can withstand the use of a caustic product, call a plumber, and if you suspect that your drain is completely clogged, don't use lye, as it will just sit on top of the clog.