Which chemical can be used to lower high free chlorine levels?

Hydrogen peroxide is a versatile chemical that can be used in pool maintenance to help lower high free chlorine levels. When added to pool water, hydrogen peroxide reacts with the chlorine, effectively breaking it down and reducing the concentration of free chlorine. This reaction is beneficial for maintaining a safe and balanced swimming environment, especially in situations where chlorine levels have spiked due to over-dosing or contamination.

While other options may have roles in pool chemistry, they do not serve the same purpose of specifically lowering free chlorine levels. Calcium carbonate is primarily used to increase pool alkalinity and stabilize pH levels, sodium bicarbonate also contributes to raising alkalinity, and potassium chloride is typically used to replace sodium in saltwater pools but does not effectively reduce chlorine levels.