Problem Entity

Green Water

Pool water discolored green by algae bloom due to insufficient free chlorine.

Definition

Green pool water is almost always caused by an algae bloom — typically green algae — resulting from insufficient free chlorine. Contributing factors include CYA too high (reducing chlorine effectiveness), missed shock treatments, heavy rain (diluting chlorine), extended periods without service, or pump failure. Treatment involves lowering pH to 7.2 to maximize chlorine activity, brushing all surfaces, shocking to 30 ppm FC, and running the filter 24 hours. The water may turn grey as algae dies, then clear over 24–72 hours as the dead algae is filtered out.

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