As I thought Calcium Carbonate was the usual calcium increaser I wondered if Calcium Chloride releases its chlorine into the water as well.

As a vinyl pool owner I've only ever used Calcium Hypochlorite as either a convenient shocking agent or in a failed attempt to use the junk HTH tablets as a slow-release method of chlorination.

We were going away and I didn't want the increase in CYA and decrease in acid from tri-chlor tabs. The tabs turned to a clogging paste in my skimmer in less than 12 hours, rather than the 5 days HTH claimed. HTH had stopped making the capsule-enclosed version. (I think PoolLife or someone still makes them).