Fat (triglyceride) + 3 NaOH → glycerol + 3 soap molecules (sodium salts)
| 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. |
Outside drains often have standing water or unknown contents. Always wear full PPE: chemical-resistant gloves, goggles, face shield, long sleeves, and boots. caustic soda for outside drains
If you choose to use it, follow these strict safety protocols:
This article provides a comprehensive guide on when to use caustic soda, how to use it safely, and when you should opt for alternative solutions. What is Caustic Soda and Why Use It? Fat (triglyceride) + 3 NaOH → glycerol +
Report prepared for educational purposes. Always follow local regulations and product safety data sheets (SDS).
For liquid caustic soda (20–30% solution), pour 500ml directly, wait 30 min, then flush. | | Cast iron | High | Heat
If you choose to use caustic soda on an outside drain, have a garden hose ready with cold water, keep pets/people indoors for 2 hours, and neutralize any spill with vinegar immediately. Better yet, call a plumber – the cost of one chemical burn emergency room visit far exceeds a service call.
Carefully pour the hot solution directly into the blocked outside drain. Do this slowly to avoid splashing.