Water Testing Equipment and Methods

Colorimetric analysis
Photometric analysis
Electrochemical methods (Redox and Amperometric)

Chlorine
Bromine
pH
Alkalinity
Ozone
Calcium Hardness
Chloride
Sulphate
TDS (Total Dissolved Solids)
Langelier Balanced Water Index

Water Testing Equipment and methods

Notes on Sampling

It is very important that a representative sample of the pool or spa water is taken for analysis so
• always take the sample from the same place. This is generally best at the furthest point from the return to the pool of the freshly disinfected, filtered water.
• take the sample from approximately 300 mm below the surface and slightly away from the side of the pool.
• always rinse the sample container several times with the water before taking the sample for testing.

Colorimetric Analysis

This method of water analysis is by far the oldest and simplest way of determining the concentrations of anions and cations in water. In it’s applications to swimming pool and spa water analysis it was established well over half a century ago that by adding a selective reagent to a sample of water a colour was produced, the intensity of which was proportional to the concentration of chlorine in the water. Calibrated colour standards were produced, some in transparent plastic material, others in glass, against which the coloured test solution was matched to give the result of the analysis. These two systems are still in use today with the plastic colour standards usually in the cheaper, less robust, test kits, while the glass colour standards tend to be in the better designed, professional kits developed for public pools and leisure complexes.
It is with this latter type, the chemically produced glass standards, which we are primarily concerned and have been produced for the pool market for over 60 years. These are designed for accurate visual analysis :
• accurately calibrated glass colour standards, guaranteed non- fading even under extreme conditions.
• a Comparator unit which accepts discs, cassette-style, ensuring very perfect location every time and which has an in-built optical prism unit to bring the two fields of view – test solution and glass colour standard – adjacent to each other for accurate colour matching.
• a complete reagent system based on tablets. These have been shown to be the most reliable and consistent in reagent preparations.

An important point worth mentioning and often overlooked by operators is that for accurate results to be obtained when using this type of equipment, the correct lighting conditions should be used.

Photometric Analysis

Modern technology has brought the field of electronics to pool water testing and the use of portable photometers is becoming widespread.
These are instruments which pass a beam of light through the coloured test solution
onto a photodetector. The intensity of the light collected is then converted, by the microelectronics, into a value of concentration which appears in a digital display.
Hence, in this method of analysis, there is no colour matching for the operator to do, and providing the test procedure is followed exactly and some very important factors are noted, photometers can give very accurate test results.