While lye can be a helpful household product, it is also quite dangerous. Lye, also known as caustic soda or sodium hydroxide, can cause burns, blindness or other serious injuries if mishandled. It can be fatal if swallowed. If you use lye in your home, whether for making soap or clearing drains, you must be aware at all times of its highly caustic nature. It is important that you handle it carefully and dispose of any leftover lye properly and safely.
Consult your the hazardous waste collection agency locally, for specific disposal instructions for your area. Lye is considered hazardous waste and is subject to federal, state and local disposal regulations.
Do not pour lye down the drain, into a toilet, storm sewer, on the ground, or put it in your trashcan to go out with your day-to-day trash.
Wear long sleeves, long pants, protective goggles and gloves when handling lye. You may also want to wear a dust mask, as inhaling lye dust or fumes is dangerous.
Do not pour water into lye, as doing so can cause a serious reaction. Water in lye causes a chemical reaction that generates heat that can reach combustible and even explosive temperatures. Do not attempt to wash lye down a sink with water.
Use the utmost caution when handling lye. Do not allow it to spill or splash.
Keep lye away from children and animals. This includes the disposal of lye: Do not dispose of lye in a place that is accessible to children, animals unsuspecting adults.
Transfer unwanted lye into a container made of stainless steel for disposal. Make sure the container has a tight-fitting lid. Do not store or dispose of lye in any container made of plastic, cast-iron, iron or aluminum, as lye corrodes these materials.
Do not reuse the container in which you were storing the lye for anything other than storing lye.