BoUND Caustic Soda Flakes is a highly corrosive and powerful agent that can be used to unblock clogged pipes, sinks, drains, and Sewers. Directions: Add hot water to the basin or plunge hole. For basins, add a tablespoon of caustic soda flakes. For drains use about half a cup. Watch for possible backsplash or vapors when adding caustic flakes, make sure to wear appropriate PPE. Leave the caustic soda to dissolve completely and flush with hot water once again for best results. However since the use, storage and application are beyond our control, no guarantee expressed or implied is made to the efficacy of such use