BRINGING THEM TOGETHER
So there you have them: the five fickle factors that contribute to balanced spa water. As you may be thinking, maintaining perfect water balance can be tricky at times. However, the main factor you’ll be concerned with is pH, which is easy to monitor and adjust.
For those who take their water chemistry seriously, a mathematical formula can help you better understand the intricate relationship among all of these factors. Called the saturation index, it was derived from the work of Wilfred F. Langelier, who was commissioned in the 1930s to discover a method for laying down a thin layer of scale on the water-distribution piping of a large city to protect
the cast-iron pipes from corrosion. Applied to spa water, the index looks like this:
SI = pH + TF + CH + ALK – CONSTANT
SI = saturation index pH = measured pH TF = temperature factor CH = measured calcium hardness ALK = measured alkalinity minus cyanurate alkalinity, which is the alkalinity attributed to cyanurate acid, sometimes used to stabilize pH CONSTANT = combined factor that corrects for temperature, as well as the strength and concentration of ions in the water
Water is considered balanced when the SI equals zero. An SI of +/-0.3 is considered acceptable. Above 0.3 indicates that conditions are ripe for cloudiness and scaling; below -0.3 warns of possible corrosive conditions.
This type of advanced mathematics could drive the typical spa owner to rethink his or her purchase. Fortunately, at least one company has produced a simple-to-use tool that does the math for you. Developed by Taylor Technologies, the Watergram is simply two circular charts, one small and one large, laid together and riveted through the center. The small inner circle is printed with numbers for pH and calcium hardness, while the outer circle has numbers for total alkalinity and temperature. Let’s say you’ve measured the pH and taken the temperature of your spa water. You’d locate that pH reading on the inner wheel and the temperature reading on the outer wheel. When you turn the inner wheel so that the pH reading and the tem-
perature reading are aligned, the wheel shows you whether total alkalinity or calcium hardness needs to be adjusted.
As mentioned previously, test strips are a convenient and simple way to get an adequate reading on pH and total alkalinity. Plus, most test strips also have pads to test the level of chlorine or bromine sanitizer in the water, making them a quick and efficient way to stay on top of your water quality.
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