Actaully Jim, there's two main compounds used to dechlorinate. The most common actually isn't S.T. but rather the active ingredient in ChlorAmx. S.T. IIRC doesn't touch chloramine that well, so many major manufacturers have gone to: http://www.reed-mariculture.com/cloram%2Dx/msds.pdf Also, T.S. comes in a major gradient of grades, be carefull what you buy. Some have particuluates that need to be removed (even in photography grade materials).