One of the most common chemicals used for the prevention of chlorine loss in swimming pools is Cyanuric Acid (also called CYA, Conditioner, or Stabilizer); it protects the free chlorine from being destroyed by the sun ultraviolet rays. Because of this, cyanuric acid can help reduce the cost of maintaining a safe and clean swimming pool.
Areas exposed to high levels of sunlight should maintain 40-60 ppm (parts per million). Once CYA reaches 90 it will drastically reduce the effectiveness of your chlorine. The typical ratio of chlorine to CYA is 1-10, meaning if your CYA is 40 you will need your chlorine to be 4.0.
What If Too Much CYA Is Present?
What could happen when you have high levels of cyanuric acid? The first issue would be the efficacy (effectiveness) of the chlorine to act as a disinfectant. Higher levels will bind with the chlorine (Chlorine Lock), making it slower acting to kill bacteria and micro-organisms, and prevent algae. You will typically experience Yellow Algae in the spring and fall and cloudiness in the pool water. When Algae is present pool owners typically shock the pool with more chlorine which contains stabilizer. This can make the situation worse and cause extreme frustration when the pool doesn’t clear up. High CYA will increase the cost of chemicals required to sanitize your pool.
Why Did This Happen?
Pool owners that utilize powered, tablet, or stick forms of stabilized chlorine will be adding cyanuric acid unknowingly, as most of the chlorine sold today contains cyanuric acid. Continual use of these products without regular water exchange will increase the cyanuric acid to a high level.
Resolving High CYA Levels?
1. At this point, it would be recommended that a portion of the pool water be replaced with fresh water, as there are no other proven means of reducing the cyanuric acid in pool water. Typically, it is recommended to replace 1/3 of the pool water each season when using chlorine as your sanitizer.
2. Run your pool pump longer. It will take your pool longer to filter and sanitize your water. Consider running the pump 12-16 hours each day when your CYA is over 90. At the first sign of Algae run the pump 24 hours after treatment until the water clears.
3. Change your method of sanitation . Consider using liquid chlorine or consider changing to a salt system.