What is DE?

[CarlD]

There are several grades of DE: Pool, Horticultural, Food, etc. I'd use only pool grade in your pool filter to be safe (though I have no idea what would happen if you used another grade).

As Carl said, pool stores will have the right stuff. So will Wal-Mart, Home Depot, Lowes, etc. (in the pool season).

Thanks. I only know about pool DE. Even at expensive stores it's fairly cheap, especially if you plan on using it to augment your sand filter. As I said, one 10# box was $8 and I've barely used half in 2 seasons.