Your test strip says chlorine is fine \u2014 or even high \u2014 but your pool water is still green. Before you dump another bag of shock in and hope for the best, stop. High chlorine readings with green water almost always mean one of five specific problems, none of which are solved by adding more chlorine. This article explains exactly what’s going on and gives you the step-by-step fix.<\/p>\n
Here’s the core issue: your test kit measures total chlorine<\/strong> or free chlorine<\/strong>, but it doesn’t tell you whether that chlorine is actually working<\/em>. Chlorine can be present in your water and completely ineffective at the same time. That’s the frustrating reality behind the “chlorine is high but pool is green” problem.<\/p>\n Think of it like fuel in a car. You can have a full tank, but if the fuel line is blocked, the engine won’t run. High chlorine readings with green water means your chlorine is either neutralized, chemically locked, or fighting a losing battle against an established algae colony.<\/p>\n Let’s go through every cause \u2014 starting with the most common.<\/p>\n —<\/p>\n This is the number one culprit, and most pool owners don’t even think to check it.<\/p>\n Cyanuric acid (CYA) is a chlorine stabilizer that protects chlorine from UV degradation. At the right level \u2014 30 to 50 ppm<\/strong> \u2014 it’s essential. But CYA accumulates every time you use trichlor tablets or dichlor shock, and once it gets too high, it chemically binds to your chlorine and prevents it from working.<\/p>\n This condition is called chlorine lock<\/strong>. Your test kit shows chlorine present \u2014 because it is \u2014 but that chlorine is bound to CYA molecules and can’t sanitize anything. You can have 5 ppm of “chlorine” that’s functionally doing nothing.<\/p>\n The math:<\/strong><\/p>\nCause #1: Cyanuric Acid Is Too High (Chlorine Lock)<\/h2>\n
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