Shock
Shock is the practice of adding a large dose of chlorine or oxidizer to pool water to reach breakpoint chlorination, kill algae, or reset water clarity.
Definition
Shock is the practice of adding a large dose of chlorine or oxidizer to pool water to reach breakpoint chlorination, kill algae, or reset water clarity.
Typical Values: Standard shock target: 10 ppm FC; Green pool recovery: 30 ppm FC
In Plain Language
Pool shock products are typically calcium hypochlorite (65–73% available chlorine), sodium dichloro-isocyanurate (dichlor), or sodium hypochlorite at high concentration. Shocking raises free chlorine to 10 ppm or higher — far above the normal maintenance range. Non-chlorine shock (MPS) is used specifically to oxidise organic material without raising free chlorine.
Why It Matters
Weekly shocking is a preventive maintenance practice that destroys chloramines and oxidises organic contaminants before they accumulate to problem levels.
Typical Values
Standard shock target: 10 ppm FC; Green pool recovery: 30 ppm FC
Last reviewed: 2026-06-01