I have a small jar of powdered Potassium Metabisulfite and Campden tablets that are Sodium Metabisulfite. The tablets are 550mg. I have seen on this forum that these chemicals, when added to your brewing water, dechlorinate and remove chloramine. But how much? I have seen that one tablet does 20 gal but I have to imagine that one tablet's mg content can vary. The Potassium is in powder form, how much of that ought to be used? I am an all grain brewer and I brew 5 gal batches starting with about 7-8 gal. My question: If I used the Potassium, how much should I use? If I used the campden tablet (550mg), should I use a whole tablet or half? I do realize that this has been answered (sorta), but I need more specifics.