Dichlor/trichlor????

[JohnT]

Thank you; I understand now! One more question: Can someone give me a link to Ben's calculator I've seen mentioned here?

Not Ben's calculator, but Michael Smith's (mwsmith2) calculator.
http://home.earthlink.net/~mwsmith70/data/BleachCalc262.exe


PC only as far as I know.

[Ohm_Boy]

Beyond the bleachcalc program (which calculates much more than bleach dosages) there is Ben's "best guess" chart, which you will find as a sticky in this forum. It gives guidelines for chlorine levels and shock levels for various levels of CYA.
It's valuable because, while CYA keeps all the chlorine from going away from UV exposure, it also tends to "lock away" some amount of the total chlorine in the process, requiring more to fully sanitize at higher CYA levels. There's science... I mean... magic... or maybe magic science, involved, but Ben's chart helps to make it simple.