Dichlor is about 50% cyanuric acid by weight.
Dichlor is a stabilized chlorine commonly used in hot tubs. The problem is hot tubs don’t need to be stabilized. They are not out in the direct sun all day like pools so they don’t need the UV protection that the cyanuric acid in Dichlor offers.
By weight, dichlor contains about 50% CYA. That means that for each 10 ppm of chlorine added to the water from dichlor, the CYA increase is 9 ppm.
Each person per hour in the hot tub will consume 4 grams of pure chlorine or 8 grams of dichlor which is 3.5 ppm of chlorine in a 300-gallon hot tub. So 2 people using the hot tub 2 times a week will consume 14 ppm chlorine and increase the CYA by 12.6 ppm per week. More times of use or more people using the tub would require more chlorine and have a larger increase of CYA.
The bottom line is that at that rate, CYA is building fast and in a very short time will lead to issues no hot tub owner wants to experience.
The good news is FROG has a solution – it’s called FROG @ease with 0% CYA.