Active IQ Level 2 Award in Pool Operations (sample manual)

Section 9
The essential tests to ensure optimum pool water quality
Typical procedure
1 Switch the photometer on using the on/off key.
2
Select the appropriate mode (e.g. free chlorine or pH) by pressing the mode key or the appropriate button
on the keypad.
3
4
5
Fill a clean test cell with 10ml of test water, aligning the triangles on the test tube with those on the
photometer, and press the zero/test key.
Add the appropriate reagent tablet (e.g. phenol red to measure pH).
Crush the tablet and make sure it has properly dissolved; screw the cap back on.
6 Place the test cell in the test compartment, once again aligning the triangles, and press the zero/test key.
7
8
The method symbol will then flash and the result will appear in the display panel.
Remember to repeat the zeroing process in between each test.
A photometer will only measure within its individual range, so if the sample is either below or above this range, an
error message will be generated. If it is above range, it will be necessary to carry out dilution of the sample until the
sample comes back within the range of the instrument.
When measuring chlorine levels using a photometer, the principle of dissolving the DPD 1 into two drops of water
and then making it up to 10ml should also be followed, and it is still necessary for the operator to leave two minutes
for the chemical reaction to take place between the DPD 1 and DPD 3 in order to establish the total chlorine reading
from which the combined chlorine level is derived.
Newer photometers have a built-in timer which will count down
from two minutes when the operator indicates that they are
working out a total chlorine reading.
Where the water has a high calcium content, it may be
necessary to use DPD 1 high calcium tablets.
Photometers are precision instruments but they must be
checked against calibration standards to ensure that they are
properly calibrated. Some photometers have to be returned
to the manufacturer for recalibration, whereas others can be
recalibrated by the user.
Cyanuric acid test
Figure 9.6 Calibration standards
If the pool is treated with ‘stabilised chlorine’ (i.e. chlorine that contains cyanuric acid, e.g. trichlor), it is also
necessary for the cyanuric acid levels to be tested on a weekly basis. Most photometers will measure cyanuric acid
levels; the typical procedure is followed, except that a cyanuric acid test reagent tablet is used. The recommended
range for cyanuric acid is between 50 and 100mg/l. If the pool operator does not use a photometer, it is still
possible to measure cyanuric acid levels using the turbidity test method.
The turbidity tester consists of two plastic tubes: an inner tube, which is graduated, and an outer tube, which has a
water level indicator. A cyanuric acid tablet is dissolved in the sample, and if there is any cyanuric acid present, the
sample goes cloudy. The inner tube is then pushed into the outer tube until a black spot on the bottom of the inner
tube disappears. At this point, the reading on the inner tube at the interface with the water is noted, and from this
the cyanuric acid level can be determined.
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