First Choice Cal-Shock Calcium Hypochlorite

This product is a calcium hypochlorite shock treatment designed to sanitize your pool water by eliminating harmful bacteria and contaminants, which helps restore water clarity.

While it is fast-acting, you should always wait until the chlorine levels return to a safe range—typically between 1 and 4 ppm—before re-entering the pool. It is recommended to test your water chemistry after application to ensure it is safe for swimmers.

First Choice Cal-Shock is effective for most standard pool systems, but because it is a calcium-based chlorine, you should monitor your calcium hardness levels if you have a plaster or concrete pool to prevent scaling.

Store the pail in a cool, dry, and well-ventilated area away from direct sunlight and moisture. Always keep the lid tightly sealed and store it away from other pool chemicals to prevent dangerous reactions.

The powder should be broadcast evenly across the surface of the pool, preferably in the evening when the sun is down to maximize its effectiveness. Follow the specific dosage instructions on the label based on your pool's total gallon capacity.