When you put the cya in the skimmer it goes directly into the filter, it takes a while to dissolve, so you can't backwash for a week, or you may backwash the cya right out. That is the advantage of not putting it in the skimmer. If you just put the cya in the pool, it will lay all over the bottom until it dissolves, that is the advantage of the ingenious inventions on this forum!