Caustic Soda For Outside Drains !!better!! Jun 2026

Caustic soda (sodium hydroxide) is one of the most effective DIY solutions for unblocking outside drains, grease traps, and gullies. It works by creating a chemical reaction that turns fats and organic matter into a soap-like substance (saponification), dissolving the blockage.

| Pipe material | Resistance to NaOH | Notes | |---------------|--------------------|-------| | PVC (uPVC) | Moderate | Safe up to 10% conc. & <60°C; high heat may warp. | | ABS | Moderate | Similar to PVC, but softer. | | Cast iron | High | Heat cycles can crack old brittle iron. | | Copper | Low | NaOH attacks copper over time (blue-green corrosion). | | Galvanized steel | Very low | Rapid corrosion, pinholing. | | Concrete/Clay | High | Safe but heat + cold water can crack clay. | caustic soda for outside drains