What is CYA?

[PatL34]

To add to what JohnT said, CYA also controls as to when the Chlorine is needed. However, too strong a concentration, say 100 ppm, wiil prevent the chlorine from being fully utilized. Too low a concentration, say <20 ppm and the chlorine will evaporate before it can be used.

Ben, the moderator of this forum created a chart to help newbies and oldies to get an idea of how much CYA to add, based on the Chlorine level:

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

FC = Free Chlorine. This is the value that does the sanitizing so to speak.

Hope this gives an insight as to what CYA does.

Pat