CYA 230, replaced 1/2 of water...now 217???

[rbonin]

The catch with stabilizer is that at higher concentrations, it renders chlorine less effective at sanitizing. Here is a chart that is popular on this site:

Stabilizer . . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm ... . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

You can see that at your current CYA concentration, you will have to maintain at least 8ppm free chlorine for effective sanitizing. I think most on this site would recommend you shoot for 30-50 ppm CYA, but I guess it depends on how much sun your pool gets. I keep mine at 40ppm and mine is in direct sun all day.

~Rick~