What is the active ingredient in Drano?

• A. Hydrochloric acid
• B. Sodium carbonate
• C. Sodium hydroxide
• D. Potassium hydroxide

Answer: (C)

Sodium hydroxide is used because it’s a strong base that rapidly breaks down organic matter in clogs. It does this mainly through saponifying fats (turning grease into soap) and hydrolyzing proteins, which dissolves the gunk that blocks drains. The heat generated by the exothermic reaction also helps loosen the obstruction, making the drain easier to clear. This caustic action is what makes Drano effective for freeing blocked pipes, which is why sodium hydroxide is the correct active ingredient.

Hydrochloric acid would be highly corrosive and pose greater risk to pipes and safety, so it isn’t the active component in Drano. Sodium carbonate is milder and not as capable of aggressively dissolving tough organic clogs. Potassium hydroxide is another strong base that could perform similarly, but the standard Drano formulation centers on sodium hydroxide, which is why that option is the correct match.