COLUMNIST
R elax by the pool knowing it is safe
By Bruce Hope
to swim
C hinese New Year, like every other festive celebration throughout the year, is a great chance for
family and friends to gather together. Pools are a natural magnet for younger members of the family
to enjoy. As a parent, naturally you will be concerned that the pool is safe to swim in.
The easiest way to ensure it is safe is to check
whether the water has been disinfected and
tested. Not all of us carry a test kit in our car
so sometimes it is a challenge. Many hotels
such as the Shangri-La Kuala Lumpur test
the water frequently during the day and
display the test results up on a board. This
makes it easier as a guest to know.
The most frequent tests are free chlorine
and pH. These two parameters have the
most impact on bathers. Free chlorine is
the chlorine that is available to kill any
pathogens (bugs and bacteria). The ideal
range is 0.5ppm to 1.5ppm of chlorine. A way
to visualise this is around half a teaspoon
of chlorine per cubic metre of water. If the
chlorine is lower than this then it may not
kill any of the bacteria. If it is higher, then
people who are sensitive to chlorine may
feel some minor skin or eye irritation.
For pH, the ideal range is 7.2 to 7.6. The
reason for this is that the human eye
generally has a pH of around 7.4. Keeping
the pool water between 7.2 and 7.6 helps
avoid bather eye irritation. From a water
chemistry perspective, it is better to have
the water as close as possible to 7.2 as
chlorine effectiveness is much higher.
Free chlorine is the combination of Chlorine gas (Cl2), Hypochlorous Acid (HOCl) and Hypochlorite
ions (OCL-). The most effective disinfectant is Hypochlorous Acid. As you can see from the graph, the
availability of HOCl drops dramatically between pH of 7 and 8.
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