Watermaid ecoblend Owner's Handbook Manual page 27

Because of its instability, chlorine has a half-life of some 35 minutes in strong sunlight and even less in the
presence of contaminants. Therefore, the use of a chlorine stabiliser is strongly recommended for outdoor
pools as it lengthens the half-life of chlorine to about 140 minutes and helps maintain a residual of chlorine in
the pool on hot sunny days. At the beginning of the summer season, chlorine stabiliser (isocyanuric acid)
should be added to outdoor pools. Please refer to the product label for the required quantity to add.
The pool should be topped up with chlorine stabiliser throughout the hot summer period to maintain a level
between 30 and 50 ppm. Do not exceed 80 ppm.
Factors such as, sunlight, filter and pump efficiency, stabiliser level, bather load, debris, water temperature,
salt level, water level, chemical balance and age of the cell, all affect the final chlorine level.
PH is a measure of the concentration of hydrogen ions in a solution, or in simpler terms the acidity or
alkalinity of a solution. A solution with pH 7 is neutral; below 7 is acidic; and above 7 is alkaline.
By electrolysis, the WATERMAID® cell produces sodium hypochlorite (NaOCl), which in water dissociates into
sodium (Na+) and hypochlorite (OCl-) ions. It is the hypochlorite ions that then form with the hydrogen (H+)
ions (from the water) to form hypochlorous acid (HOCl), the active agent that destroys bacteria and algae,
and oxidizes organic matter.
The chart (right) shows the effect of pH on the
reversing reaction of hypochlorous acid in water.
The greater the
hypochlorous acid molecules in the water, the
better the sanitising effect.
It can also be seen that at pH between 3 and 7,
the percentage of active hypochlorous acid
molecules in the water is at its highest, although
it is not suitable for swimming because the water
is acidic. And at pH 8.0, the chlorine in the water
is only 21% effective.
Marblesheen, pebble, quartzon and tiled pools stabilise naturally between pH 7.6 and 8.2 so the effects of
chlorine are disadvantaged. For these pools it is recommended that "pH buffer" (sodium bicarbonate) be
used as this will help stabilise the pH between 7.6 and 7.8, as well as raise the total alkalinity. Please refer to
the product label for the quantity required.
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Version 20170223
percentage of active
The ideal pH range for swimming conditions is between 7.2
and 7.8.
A pH above or below the ideal range can also cause irritation to
the eyes and skin.
c) pH
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