There are several different methods pool pros use for water testing, and each comes with its own set of advantages and disadvantages. These methods include:
• Photometers and reagents.
• Titration reagents.
• Comparator test.
• Test strips. Among these methods, photometric testing stands out as the most precise. This approach utilizes reagents and photometers, eliminating the subjectivity associated with visual color matching. Instead, it measures the transmission of light through a water sample after it has been treated with a color-altering reagent. By quantifying the difference in light transmission before and after treatment, this method achieves remarkable accuracy, often with a resolution of 0.01 parts per million (ppm).
Another method, colorimetric titration, relies on chemical reactions to change the color of a water sample, which is then analyzed by the pool operator to determine its concentration. While cost-effective, this method demands a certain level of technical proficiency, including the ability to discern subtle color changes, precisely administer reagents, and perform rapid calculations on site. Typically, the resolution of these tests falls within the range of 0.2 ppm to 20 ppm, depending on the specific kit and parameter being assessed.
Similarly, the color comparative method offers affordability and widespread acceptance in commercial testing. However, it suffers from stability issues, requires keen visual acuity, and provides only modest resolution, typically around 0.4 for pH and 1 ppm for chlorine.
For home use or residential pool maintenance, test strips are a common choice due to their convenience, affordability, and shelf stability. Although they offer a quick and straightforward screening option, they lack precision and demand adeptness in color matching. Typically, the resolution of test strips hovers around 0.4 for pH and 1 ppm or higher for chlorine.
Overall, photometric analysis emerges as the gold standard for water quality assessment. Modern photometers have simplified field testing and, in some cases, can be competitively priced when factoring in the initial investment.
La Motte’s ‘Color Q’ Photometer
