If you add bleach to gain chlorine, why would you want to add cal-hypo afterwards? As a source of chlorine, you wouldn't need to use them both on the same day. When I said that many people use both, I didn't mean in the same day as that is not needed. What I meant was that some people might use bleach most of the time and then only use cal-hypo occasionally instead of bleach or vice versa. Does that make more sense?