As stated before, total alkalinity tells you how many alkaline substances are in the water. In pool or spa water, this should be bicarbonate alkalinity. You want the alkalinity in a range of 80 ppm to 120 ppm.
Alkalinity measures the resistance of water to changes in pH. This is done through the presence of the carbonate ion family. It should have enough carbonate ions to stabilize the pool chemicals, but not so much that scale will form.
Under ideal pool conditions (pH 7.2 to 7.6), most of the carbonate is in the form of bicarbonate with a small amount of carbonate ions to provide saturation. When total alkalinity is measured with the test kit or test strips, it is considered, for practical reasons, to be equal to the alkalinity of carbonate.
If you add sodium carbonate (sodium carbonate) to the pool water, it will increase the total alkalinity because it will add carbonate ions, but it will cause large variations in pH and it will be more difficult to control the pH. If you use baking soda, it will also increase the total alkalinity, but it will not change the pH much. If you need to add a large amount of baking soda, you should do so at a rate of about 2 pounds of chemical per 12,000 gallons of water every 3-4 days.
1.5 pounds of baking soda will raise the total alkalinity about 10 ppm in 10,000 gallons of water. Therefore, to increase the total alkalinity of a 25,000 gallon pool by 10 ppm, you will need 3.75 pounds of baking soda. And to raise a 2,200 gallon spa to 10 ppm, you’ll need about 1/3 pound of baking soda.
Increasing total alkalinity can be a time-consuming process, but once you’ve done it, it usually won’t change much over time in a well-maintained pool. It is important that you adjust the alkalinity before adjusting the pH as it has a great effect on the pH and how it behaves.
While overall total alkalinity should be between 80 ppm and 120 ppm for pH buffering and carbonate saturation, the lower end is best for spas and the upper end for gypsum pools. Too low will cause plaster pool etching, metal corrosion, and eye irritation due to unstable pH. If it is too high, it can cause the pool to become cloudy, an increase in the use of acid to adjust the pH, and a loss in chlorine efficiency.
Since reducing total alkalinity is also a time-consuming process of slowly adding acid to the pool, it is best to bring the pool slowly to the correct level so as not to “shoot too much” where you want it to be, when needed. adjusted, you can now proceed to adjust your pH to the required values of 7.2 to 7.6. Adjusting the pH will be your second step in producing the chemicals in your optimal pool.