Free available chlorine
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(Redirected from FAC)
Free Available Chlorine (sometimes abbreviated as FAC or FC) - The portion of the total chlorine remaining in chlorinated water that is not combined with ammonia or nitrogen compounds and will react chemically with undesirable or pathogenic organisms. The most active disinfectant in pool/spa water.
This is a combination of hypochlorous acid, hypochlorite ions, and chlorine associated with cyanuric acid. It is formed when a chlorine sanitizer is added to pool or spa water.
To maintain proper sanitation, the FAC should be maintained at between 1.0 and 3.0 ppm. The combined chlorine level should never exceed 0.2 ppm, and ideally should be 0.0 ppm.
