Try 20 Mule Team Borax, its much cheaper and for works just as well if you mix it with hot water. Walmart has its own brand, I believe and its usually in the washing detergent section.
I didn't realize they were the same.....that will make it easier for me. Finding Calgon in our area is usually impossible, sometimes just difficult. Our local grocery chain does not carry any Calgon products and I have had the same experience as Roy....one time WalMart has it, next time not. The times they have had it it was liquid.
Travel Safe!