English Instructor Manual (PDF) - Metric Version - National ...

Key Points: Explain that chlorine is the most common disinfectant used in commercial pools.
While chlorine may not be the best disinfectant or the best oxidizer or the best algaecide, it is very
good at all three and is one product. Explain that chlorine is present (percentage listed with each
compound) in the following compounds commonly used to disinfect pools:
Chlorine gas (100%)
Calcium hypochlorite (65%-78%)
Sodium hypochlorite (10%-12%)
Lithium hypochlorite (35%)
Trichlor (90%)
Dichlor (56%-63%)
Key Points: Discuss that chlorine compounds fall into two categories. These include:
Organic chlorine compounds, such as trichlor and dichlor, contain cyanuric acid as part
of the compound. They are considered stabilized chlorines.
Inorganic chlorine compounds, such as calcium hypochlorite, sodium hypochlorite,
lithium hypochlorite, and chlorine gas, do not contain cyanuric acid as part of the
compound. They are considered unstabilized chlorines. However, these chlorines can
be stabilized by adding cyanuric acid to the water as a separate product.
Key Points: Discuss the use of stabilizers to increase the stability of chlorine in pool water.
These include:
Stabilizers decrease the breakdown of chlorine due to UV light.
The stabilizer for chlorine is cyanuric acid.
The ideal range for cyanuric acid levels is 30-50 mg/L.
Local health codes may restrict the use of cyanuric acid in public pools or spas. It is
important to check the local code.
Key Points: Discuss the chemistry of chlorine. Explain that when a chlorine compound is
introduced to water, the chemical reaction forms:
Hypochlorous acid, which is the active killing form of chlorine in water.
Hypochlorite ion, which is an inactive form of chlorine in water. By-products specifi c
to the type of chlorine used. For example, the by-product of sodium hypochlorite (liquid
bleach) is sodium chloride (table salt).
Free Chlorine, sum of hypochlorous acid and hypochlorite ion.
Combined Chlorine, reaction of free chlorine with inorganic and organic compounds in
the water
Key Points: Discuss the most common stabilized disinfectants and their chemistry:
Trichloro-s-triazinetrione – commonly called trichlor
Sodium dichloro-s-triazinetrione - commonly called dichlor
Key Points: Discuss the various aspects of bromine. These include:
There are two methods of using bromine. The most common is bromine tablets
(BCDMH). The second is sodium bromide, which must be used with potassium
monopersulfate. Potassium monopersulfate is a non-chlorine oxidizer.
While bromine is a strong disinfectant, it is not as good as chlorine as an oxidizer.
Because of this, the use of a supplemental chemical for oxidation is occasionally
needed.
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© 2014 National Swimming Pool Foundation®