When To Shock

[crystolsbrown]

My CYA level is at 30, if I maintain a FC level of 5ppm is there any reason to shock weekly, monthly ???

[DavidD]

You should only shock when your CC (combined Chlorine) gets above .5 ppm. Now if you were to have an algae bloom or cloudy water due to a bunch of kids, you may elect to shock but in both of these instances your CC would probably be higher than .5. Most pool stores tell people to "shock" weekly to A) sell more chemicals and B) because most people don't or can't test their water so they figure it's the "safe" thing to say.
Remember, FC (free chlorine-good) + CC (combined chlorine-bad) = TC (total chlorine)

Dave