C) Ph; The Chemistry Involved - Watermaid WM10LED Owner's Handbook Manual

The following is a list of possible causes to commonly encountered problems.
CHLORINE RESIDUAL LOW OR NIL
* Not enough chlorine being produced [refer to section 7(i)]
* Heavy bather load - insufficient running times to cope [refer to section 9]
* Strong sunlight conditions and/or insufficient chlorine stabiliser level [refer to section 1(b)]
* pH too high or low [refer to section 1(c)]
* Poor water circulation [refer below]
* Algacide has been added within the last 4 weeks [refer to section 12]
* Excessive calcium level causing scale on Cell electrodes [refer to sections 5 & 7(iii)]
* Cell is old and needs replacing [refer to section 7(v)]
CHLORINE LEVELS HIGH IN THE MORNING AND NIL AT NIGHT
* Heavy bather load [refer to section 9]
* Extreme sunlight conditions and/or insufficient chlorine stabiliser level [refer to section
1(b)]
RED LIGHT
* Nil or insufficient water flow in Cell or poor circulation [refer below]
* Problem with Cell connection [refer section 3(v)]
* Excessive calcium level causing scale on gas sensor [refer to sections 4, 5 & 7(iii)]
NO GREEN LIGHTS
* Low salt level [refer to section 3(ii) and 8]
* Excessive calcium level causing scale on Cell electrodes [refer to sections 5 & 7(iii)]
* End of Cell life [refer to section 7(v)]
* Problem inside Power Supply - refer to qualified service technician for repair
NO LIGHTS AT ALL
* No power to WATERMAID chlorinator [refer to section 3(vi)]
* Timeclock incorrectly set or faulty [refer to section 6]
* Problem inside Power Supply - refer to qualified service technician for repair
SCALE BUILD-UP ON CELL ELECTRODES [for removal refer to section 7(iii)]
* Excessive calcium level in water [refer to section 5]
* Insufficient Magnesium level in water
PH ALTERS RAPIDLY AND EASILY
* Low total alkalinity in marblesheen, pebbled, quartzon or tiled pools or spas and may be
the result of contamination [e.g. debris, urine etc][refer to section 1(c) and section 11]
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pH refers to the acid/alkaline balance of the water. pH 14 is alkaline, 0 is acid and 7 is neutral.
Within the pH range 7.2 to 7.8 chlorine will work effectively as a sanitizer, and the
precipitates formed will be at their maximum size and easily picked up by the filter.
At pH 8.0, chlorine is only 21% effective and greater than 8.0 the water is alkaline and can cause
skin rashes. Below 7.0 monochloramines are formed and will sting sensitive skin and eyes.
Marblesheen, pebbled, quartzon and tiled pools and spas stabilise naturally between pH
7.6 and 8.2 so the effects of chlorine are disadvantaged. For these pools and spas 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.
Total alkalinity is a measure of the alkaline chemicals in the water such as bicarbonates and
carbonates. Keeping the total alkalinity between 150 and 200 ppm will help keep the pH
below 7.8 (to achieve the desired total alkalinity, refer to tables, section 11).
Adding sodium bicarbonate will also help to protect newly-surfaced marblesheen, pebbled,
quartzon and tiled pools and spas, as it will react with calcium salts and form a coating of calcium
carbonate over the surface. This in turn will slow down lime leaching out from the fresh cement
(which contains up to 60% calcium oxides), thereby making it easier to achieve the desired water
balance (measured by the Langlier Index calculation, refer to section 11). For an average sized
pool, about 10 Kg (approx. 22 lb) of sodium bicarbonate will raise the total alkalinity 80 ppm.
pH remains stable for pools and spas with inert surfaces such as fibreglass, fibreglassed
concrete, painted concrete and vinyl-lined surfaces which also have a naturally
occurring total alkalinity of 80 - 100 ppm. As this is an ideal situation, there is no need
to add pH buffer to these pools or spas.
If hydrochloric acid is used to lower pH, it should be added SPARINGLY and only according to the
instructions given by an Acid Demand Test Kit, as the acid will attack the pool and spa walls
causing the calcium level in the water to rise.

2. THE CHEMISTRY INVOLVED

The WATERMAID Cell, by electrolysis, produces
sodium hypochlorite (NaOCl). In water, sodium
hypochlorite dissociates into sodium (Na + ) and
hypochlorite (OCl - ) ions. It is the hypochlorite
ions that 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.
HOCl & THE IMPORTANCE OF pH
The chart (right) shows the effect of pH on the
reversing reaction of HOCl (hypochlorous acid) in
water.
It can be seen that HOCl is more effective as a
sterilising agent at pH levels below 7. However,
for swimming conditions it is recommended
that the pH be kept within the range of 7.2
- 7.8.

c) pH

Ideal Range
7.2 - 7.8
THE EFFECT OF pH
ON THE DISSOCIATION OF
HYPOCHLOROUS ACID
100
80
60
40
20
0
1 2 3 4 5 6 7 8
pH
3
0
20
40
60
80
100
9