In Michigan, at least, only Meijers seems to have the powder Calgon. It's all I use. I only add a cup to a 2 1/2 gallon bucket of warm water and then dump that down the toilet. Even though we're stationary for the season, it seems to do the job quite well. After dumping and flushing the tank, I also let the flusher run for a couple of minutes with the valve closed to add some water back into the tank, along with what's in the bucket.