Ideal pool free chlorine range
What is Free Chlorine?
Free chlorine is the active, available sanitizer in the water that's ready to kill bacteria and algae, as distinct from chlorine that has already reacted with contaminants (see Combined Chlorine).
Why it matters
Too little free chlorine lets bacteria and algae take hold; too much can bleach liners and swimwear and irritate skin, while also being an avoidable chemical expense.
How to raise FC
Add liquid chlorine, cal-hypo, dichlor, or trichlor per the product label; most pool professionals recommend dosing in the evening to reduce rapid burn-off from UV sunlight.
How to lower FC
Let chlorine dissipate naturally in sunlight, dilute with fresh water, or use a chlorine-neutralizing product for a faster fix before swimming.
How often to test
2-3 times per week in season; daily is typical during heat waves or heavy bather load.
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Related parameters
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