Al, great idea! It should work in any type filter, as long as it's not backwashed out too soon. As a suggestion, if you don't want to go 'ballistic' with the 3#, pound it down to 'small chunks and dust' and put it in a sock (as per Janet) or a section of pantyhose or kneehigh and tie it off and drop it in the skimmer. I am doing this with the cya granuals and the dissolution rate is much quicker than just dumping it onto the pool bottom (and you don't have to worry about backwashing with it still in the filter, nor the sight of a couple #s of cya sitting on the bottom of the pool)