Sodium Hydroxide is dificult to rinse. Have to use more presure. I also noticed granules coming out the downspout. Wheter they were there before or not I didnt know. Havent noticed that since switching to sodium hypochlorite. Its the only way to go. I think I'm fortunate by my own experience with both to say that.
That caustic soda is some nasty stuff! A tiny bit goes a long way. When you use caustic soda, make sure you keep a neutralizer around. It eats through your skin!!