What You Need To Know About Alkalinity

Definition of Total Alkalinity?

Total alkalinity is the amount of bicarbonate, plus the amount of carbonate, plus the amount of cyanurate ions. It is a measure of the pH buffering capacity of water; that is, the ability of water to resist a pH change. Alkalinity is generally expressed in terms of the equivalent concentration of calcium carbonate in ppm.

Balancing Your Swimming Pools Alkalinity

Balancing pool and spa water is perhaps the most important job to make sure your pool is ready for swimming. Total alkalinity is a IMPORTANT in that process. The proper total alkalinity level in your swimming pool provides buffering so pH does not swing in and out of the proper range in response to sanitizer added. With not enough alkalinity, there will not be enough buffering and the pH may quickly drift out of the range. At high levels of alkalinity, there will be a tendency for the pH of the water to drift upward, due to the rapid escape of carbon dioxide from the water into the air. When total alkalinity is proper, these results are achieved:

  • pH
  • swimmer comfort
  • sanitizer efficacy
  • water balance
  • clarity

Salifert Carbonate Hardness & Alkalinity (Kh/Alk) Test Kit

How To Calculate alkalinity in Your Swimming Pool

1. Measure the pH
2. Measure total alkalinity (TA)
3. Measure cyanuric acid concentration (CA). If the CA is 90ppm or greater, it may be necessary to dilute the pool water sample with tap water to get an accurate reading.
4. Note the Cyanuric Acid Correction Factor in Table, based on the pH of the water.
5. Adjust the CA and subtract this result from the total alkalinity for the actual or corrected TA.
6. Formula : Measured TA — (CA x Cyanuric Acid Correction Factor) = Carbonate Alkalinity

Example: pH is 7.4. Total Alkalinity measurement (Measured TA) is 110 ppm. Cyanuric Acid level is 100 ppm.

Cyanuric Acid Correction factor at pH 7.4 is 0.31. (See table above)

Using the formula:
110 ppm — (100 x 0.31) = 110 — 31 = 79 ppm carbonate alkalinity

To Reduce Alkalinity

Total alkalinity, acid is added to the water. Approximately 2.1 pounds of sodium bisulfate (94 percent) or 1.6 pints of muriatic acid (31 percent) will reduce the total alkalinity of 10,000 gallons of water by 10 ppm.

To Increase Alkalinity

Total alkalinity, use sodium bicarbonate. Approximately 1.5 pounds of sodium bicarbonate (100 percent) will raise the total alkalinity of 10,000 gallons of water by 10 ppm.

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