Quote Originally Posted by waterbear View Post
Hope this is helpful.
Thank you, Waterbear. Until being "re-educated" by this forum I used stabilized trichlor tablets for maintaining 3 ppm chlorine and calcium hypo to shock (2 to 3 lbs.) I intend to use my remaining stock of tablets until they run out, and to shock with bleach. Soon the pool will be reopened and I'll have all the numbers. BTW, I assume that most pool owners, including bewbees, understand that "shock" is a verb. I assume you and others who remind this to us mean that just adding FC won't shock, if not done right and with the proper amount. "Ben's Best Guess CYA chart" determines the amount of free chlorine neeeded to shock a pool as a function of the CYA level. I found other publications that determine the amount of needed FC by simply multiplying the CC by 10, regardless of the level of CYA.
Here's one of these links, provided by Indiana State Health Dept http://www.in.gov/isdh/regsvcs/sanen...pool_shock.htm

Why do they ignore the CYA level and why Ben's chart doesn't use the 10 X CC rule to calculate the FC needed to shock? I'm sure that CYA and CC levels are totally independent and it seems that both chemical species should be considered when it comes to calculate the FC needed to shock.