The Center for Disease Control recommends not using cyanuric acid or products containing CYA in hot tubs or spas.
According to an article on Healthy Water from the CDC, they make a bold statement that “The CDC recommends not using cyanuric acid or chlorine products with cyanuric acid in hot tubs/spas.” The reason is the build up of CYA causes consumers to potentially soak in water that is not properly sanitized because too much CYA in water inhibits the effectiveness of the chlorine.
The Pennsylvania Department of Health in December 2016 published this statement “At even moderate levels of cyanuric acid, the amount of time it takes chlorine to kill pseudomonas aeruginosa (the bacteria that causes “hot tub itch) can be as much as a hundred times as long as in a hot tub or spa without cyanuric acid.”
These studies are recognizing what has been known in the swimming pool world for some time – that too much CYA is a bad thing. The reason is it effects the kill rate of chlorine. The kill time (CT value) for pseudomonas aeruginosa (the organism associated with hot tub rash) with no CYA is about 20 seconds. It is 1 minute and 30 seconds with 50 ppm CYA, and nearly 2 minutes with 100 ppm CYA. As CYA increases the effectiveness of the chlorine decreases.
To achieve the same kill time would require a much greater chlorine level in the water. But using dichlor you keep increasing the CYA level so it’s harder and harder to maintain the right chlorine level.
That’s what makes FROG @ease so easy! It has no CYA so hot tub owners experience consistent sanitizing power using FROG @ease with a monthly non-chlorine shock.