Raising hardness
Calcium chloride comes as 77% flakes or 94% prills. About 1.25 lb of the 77% product per 10,000 gallons raises hardness 10 ppm. It releases heat when it dissolves, so pre-dissolve in a bucket of pool water, never the other way round, and pour it around the deep end.
Lowering hardness
Only dilution lowers it. If the fill water is already hard, as it is across the Southwest, draining just resets the clock. In that case a mobile reverse-osmosis service that filters the pool in place is the real answer, and running the water balance calculator tells you whether high calcium is actually a problem yet.
Cal-hypo adds calcium
Every pound of cal-hypo shock adds about 7 ppm of hardness per 10,000 gallons. If your calcium keeps creeping up, that's why. Liquid chlorine adds none.