Quote Originally Posted by Greenfrog View Post
Thanks for the tips. I did mean NaPersulfate, not Monopersulfate.
From Wiki:
"Sodium persulfate (Na2S2O8) is a chemical compound. It is a strong oxidizer. It is a severe irritant of the skin, eyes, and respiratory system."
Potassium monopersulfate is mostly worthless, but it doesn't do much harm except to your wallet. Sodium persulfate can be a serious problem. I'm surprised the results haven't been worse.

Regarding your tester, Lamotte isn't a total junk company, but expensive is not well correlated with effective or accurate, and like I said, we haven't validated them.

Calcium hypochlorite = cal hypo IS unstabilized. But, check your label. If it doesn't say 68% (or higher) available chlorine, it's yet another mystery blend.

Given your history, I'd drain and refill. If you want to add 10 ppm CYA, OK. But no more than that. If you want to use your cal hypo AND it's unblended, that's OK too. But you have to verify it. You really shouldn't be using anything regularly except an unstabilized chlorine source (bleach or cal hypo), borax (to raise the pH) and sodium bisulfate (the sulfuric half-acid). Muriatic would be preferred if you were outdoors.