LaMotte Pool Manager Water Quality Handbook - Manual (Page 23)

Water Sanitizers
Chlorine
What Is Chlorine?
The chlorine used in sanitizing pool water is
commercially available in liquid, dry, or gas forms.
The dry form of chlorine is sold as granular, tablet, or
stick products. Any form of chlorine, when added to
water produces hypochlorous acid (HOCl).
Hypochlorous acid kills bacteria, algae, and
disease-causing organisms and is commonly referred to
as Free Available Chlorine or Free Active Chlorine
(F.A.C.). It is the killing power of free chlorine which is
important in protecting the swimmer.
The amount of free chlorine available in pool water is
significantly affected by pH, sunlight, and impurities.
A high pH level reduces the overall sanitizing power of
free chlorine, while sunlight destroys chlorine within
water. Nitrogen-containing wastes reduce free chlorine
levels by forming less active combined chlorine or
chloramines. Combined chlorine has a pungent odor
and can become irritating to the swimmer. When the
combined chlorine measures 0.2 ppm or more in a pool
it is necessary to superchlorinate or shock treat the pool
to oxidize the combined chlorine.
Several types of chlorine are used in public pools such as
gas or liquid chlorine which are added by automated
control-and-release systems.
Chlorine tablets or sticks are also used in public pools by
adding them to feeders (never add different types of
chemicals to a feeder at the same time). Listed on the
next page are the types of chlorine currently available in
the United States. Each has a different strength which is
represented by % available chlorine.
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