Is too Much Alkalinity Damaging your Pool?

January 17, 2022

Too much alkalinity in your pool can cause scaling on your surface and plumbing equipment, as well as cloud up the water. It can also disrupt chlorine, which is necessary for keeping your pool free of harmful bacteria.

It’s important to make sure your total alkalinity is in check, because it buffers your pH levels from swinging wildly as different factors change. When the total alkalinity levels get too low, there won’t be enough of a buffer to keep the pH from drifting away from its proper range. 

To maintain ideal ranges, you must keep CaCO3 (calcium carbonate) concentration within an appropriate level–one which will reduce scale build-up on surfaces or “etching.”

How often should you perform a pool water analysis?

The ANSI/APSP/ICC11 2019 American National Standard for Water Quality in Public Pools and Spas by the Pool & Hot Tub Alliance is very specific about maintaining total alkalinity. This is why pool owners are advised to perform a pool water analysis every week.

Ideally, you want between 80-100 ppm as CaCO3 to help maintain your optimal levels of disinfection efficacy while reducing corrosion.

The optimal range for alkalinity is between 100 and 120 ppm as CaCO3 because it will cause the pH to drift downwards. Although PHMB sanitizer efficacy in controlling bacteria is unaffected by total alkalinity changes, you still need to maintain an appropriate balance through regular monitoring of total alkalinity (recommended range from 80-150ppm).

How to measure and adjust total alkalinity

Total alkalinity is most often measured using test kits or test strips. 

Carbonate alkalinity can be calculated from the total cyanuric acid (CYA) and pH of pool water; however, it should always be used when calculating LSI (Langelier Saturation Index)

Total alkalinity may need to be reduced for pools that are out-of-equilibrium by adding an appropriate amount of a strong hydrochloric acid before adjusting pH or sanitizer levels. This will reduce total hardness down to where chlorine alone might not adequately provide enough sanitation.

How to Calculate Carbon Alkalinity

Sodium bicarbonate is a chemical that can be used in pools or water systems to increase the total alkalinity. A single pound of sodium bicarbonates will raise 10,000 gallons’ worth by an increment of 10 ppm (parts per million). 

This process can also be done with dichlor and trichlor sanitizers which release cyanuric acid. CYA stabilizer may also be added on its own as well since it has properties (like a weak buffer) that contribute to the overall level of carbonate alkalinity concentration.

The approximate calculation for carbonate alkaline can be done by taking 1/3 of your CO2 levels and adding it to a value that corresponds with how much chlorine you have.

By following these steps, you can generate an accurate calculation:

  1. Measure your pool’s pH, total alkalinity, and CYA concentration. If the CYA is 90 ppm or higher, you may need to dilute the pool water sample with tap water to receive an exact reading.
  2. Multiply the Cyanuric Acid Correction by its corresponding factor (based on the water’s pH):
    • pH 7.0 – factor 0.23
    • pH 7.2 – factor 0.27
    • pH 7.4 – factor 0.31
    • pH 7.6 – factor 0.33
    • pH 7.8 – factor 0.35
    • pH 8.0 – factor 0.36
  1. Get the carbonate alkalinity by subtracting the adjusted CYA from the total alkalinity.
  • TA – (CYA x Cyanuric Acid Correction Factor) = Carbonate Alkalinity

Important Alkaline Facts to Note:

  • Carbonate alkalinity is the much smaller portion of total alkaline content that affects calcium carbonate’s saturation in water. The CaCO3 saturation index, or LSI, is affected by this small amount, which can be as little as 0% to 10%.
  • Your pool’s bicarbonate level and other factors affect how well it protects your skin from a harsh environment while swimming.
  • Alkalinity and carbonate can be expressed as the equivalent concentration of CaCO3 in ppm.
  • When carbonate alkalinity is excessively high, the pH of the water can drift upward into the air due to the rapid escape of carbon dioxide.

The key to maintaining a balanced pool is the balance of alkalinity. When this parameter is properly adjusted, pH, swimmer comfort, sanitizer efficacy, water balance, and clarity are more easily maintained.

Establishing a healthy balance of alkalinity in water is also vital to the health of your swimming pool surfacing. If your pool surfacing has been affected by imbalanced alkalinity, contact Fibre Tech. Our patented fiberglass coatings are guaranteed to last 25 years, leaving your pool with a crystal white finish for decades to come! Request a quote today.

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