You can buy it on Amazon. I get mine from a place they sell industrial chemicals less than a mile from where I live. I've been using it for many years and is very cheap .I paid $20 for a kg. I use one crystal per 5 gal water. Seems it lasts for ever. I did have the recipe but lost it. It is better not to pre mix it and store it, so says the chemist that works where I bought mine.