Properly balanced water is the key to protecting your investment in pool equipment and your pool’s interior surfaces. And Total Alkalinity (TA) is a key to water balance. By definition, TA is the buffering capacity of water to resist pH changes. TA and pH work very closely together — the same treatment products (acid) that lower pH also lower TA and the same products (sodium bicarbonate) that raise TA also slightly raise pH. If TA and pH don’t work together, pool/spa water will be out of balance, leading to a wide range of problems.
It’s also important to note that TA is one of the best indicators of your pool’s overall condition. If your TA level is in the normal range, it’s a very good sign that your pool water is healthy and safe. The primary purpose of TA in your pool is to help the pH level remain stable within range and resist changes.
If TA is not doing a good job protecting pH from the additional acids or bases in the water from the treatment products, then pH moves around trying to find its place. This is referred to as “pH bounce,” which signifies a low TA environment. In other words, the water is underbuffered. You can also have an environment where there is too much TA in the water so the water is overbuffered. Having the correct TA protecting your pool’s pH is the ideal scenario.
Here are the industry recommendations for Total Alkalinity in pool or spa water:
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Minimum: 60 ppm
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Ideal: 80–120 ppm
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Maximum: 180 ppm
TA can be tricky, made up of all sorts of components such as carbonates, bicarbonates, hydroxides and cyanurates (CYA – cyanuric acid, a chlorine stabilizer). So, when you’re doing a TA test with a sample that you know for sure has cyanuric acid in it, keep in mind cyanuric acid is adding to the TA level, giving you a “false-high” reading. To get the correct TA value needed for treatment purposes and water balance calculations, you’ll need to know the “carbonate alkalinity” value. To find this value, take 1/3 of your CYA reading and subtract that number from your TA reading.
For Example:
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CYA test value = 60 ppm; then 1/3 of 60 ppm = 20 ppm (60 ÷ 3 = 20)
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TA test value = 100 ppm; then 100 ppm — 20 ppm = 80 ppm (carbonate alkalinity)
Testing for TA is simple and can be done using test strips (for a quick and easy analysis), or with a standard drop test where a reagent is added drop by drop until the sample color goes from green to red, then the number of drops used to reach that endpoint is multiplied by 10 to get the TA value. There is also a test designed to measure TA using a colorimeter.
Regardless of the method used — test strip, drop test or colorimeter — a test for TA should be performed at least weekly to ensure TA is doing its job.