Chemical Product Entity

Calcium Hypochlorite

Granular or tablet pool shock available at 65% or 73% available chlorine (cal-hypo).

Definition

Calcium hypochlorite (cal-hypo) is a dry granular or tablet chlorine compound available at 65% and 73% available chlorine — the most concentrated of common pool shock products. It raises free chlorine rapidly and is the preferred product for breakpoint chlorination and algae recovery. Unlike trichlor and dichlor, it does not add CYA. However, it does add calcium — relevant in pools with already high calcium hardness. Must be pre-dissolved in water before adding to the pool; direct application can bleach liners and damage surfaces.

Quick Facts

Units: lbs, oz
Also Known As: cal-hypo, calcium hypochlorite, granular shock, 65% shock

The source below directly supports and quantifies the calcium-addition claim (0.8 ppm calcium hardness per ppm of available chlorine added) and states this product must not be mixed with other chlorinating agents, independently corroborating (from an industry-standard fact sheet, distinct from the manufacturer SDS documents already cited on entities/trichlor-tablets.html) the trichlor/cal-hypo mixing hazard. It does not address the pre-dissolving/liner-bleaching claim above, which remains uncited on this page.