A few thoughts about CYA

[OddJob]

Ok. I just added 4lbs of cya. I put it in an old sock and hung it in front of the return jet. I tested and the black dot was *almost* invisible at 30ppm. I'm assuming I must be close to 30 since it is a definite change from no cya to this reading.

I'm not sure why I added it now ... since I've been good all summer (just lucky?). Vacation and ChemGeek have freaked me out!!

I will post a full set of numbers after we finish swimming. And I'll have to check the chart again and adjust my bleach addition accordingly.

ChemGeek, if you happen to read this far again, do you have any thoughts as to why I made it this far (since May) without CYA and no problems? I'm not being snarky, just curious.

[waterbear]

What did they do in the old days before CYA?

Good question. Historically, anhydrous ammonia had been used to stabilize chlorine since monochloramine is more stable to UV than hypochlorous acid. Sulfamic acid and sulfamates have also been used and, if I am not mistaken, so have hydantoins and other ammonia and urea like chemicals (which include cyanuric acid and cyanurates!)

It seems that chlorine/nitrogen bond that occurs has the main stabilizing effect against loss from UV light..