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

Section 9
The essential tests to ensure optimum pool water quality
The comparator
The traditional method of pool water testing for pH and chlorine uses a comparator. This is a very simple piece
of equipment where the test sample containing the reagent dye is compared against a circular disc of different
coloured pieces of glass.
Ideally, the comparator should be fitted with a portable back-light which provides good quality white light to
accentuate the colours, or it should be viewed against a bench-mounted white light source.
Figure 9.2 A comparator
The comparator should be used with the disc appropriate to the test being carried out: a pH disc (phenol red), a
chlorine disc or a disc which measures bromine levels.
If the comparator is viewed against a white light source, a more accurate result will be given.
Figure 9.3 Chlorine, pH and bromine discs
Using a comparator to measure pH
1
Select
2
Add
3
Take
4
Insert
5
Revolve
the phenol red disc and insert it into the comparator. Ensure it is installed the correct
way, with the numbers in the right hand corner of the comparator.
a 10ml sample of water to the left hand test tube.
a second clean test tube containing 10ml of water and crush a phenol red tablet into it.
the test tube containing the phenol red dye into the right hand side of the comparator.
the comparator disc until the colours match. The reading can be found in the bottom
right hand window of the comparator.
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