Last year I did an experiment with my pool and SWG and got different results than what others have experienced. I started out at 30 ppm of CYA and gradually increased it to 60 ppm and saw no increase in production of chlorine at all. My residual chlorine started out at 1 ppm and ended up at 1 ppm with the same pump run time and SWG setting. I know this is at odds with what others have experienced but I was fairly careful to do this during the spring and space out the CYA addition since it can take up to a week to fully dissolve.

Since you can only measure the chlorine residual which is a combination of SWG production and CYA retention, you cannot be sure that the increase in chlorine residual that some people experience is due to higher production. It could be that the UV exposure is high enough that they are simply increasing the retention of chlorine and thereby increasing the residual.


One thing I have noticed is a huge difference in production with water temp. This fall when the water temp dropped to 60 degrees I noticed that my production almost doubled. This is probably a combination of water temp and UV exposure but this seemed to have a much larger impact than CYA level did.

Since I have very high CH fill water, I am planning a refill soon while the CH is at it's lowest. This gives me another opportunity to repeat the same experiment and see if I get different results this time.