Looking at the numbers in Pool School it looks like there is a big difference between what is classified as a shock based on CYA and what the chem makers say a bag can do.
For example in Intheswim it says I can use 1bag per 10,000 gallons, thus for my pool I need 2 bags.
With 2 bags its a 7.7FC raise for my 20k, pool calculator/cya/FC says I need 58oz for my 14FC raise (50CYA) --- 3.5bags.
I figured out their math only works with a CYA of 20. Am I just wasting money if I dont shock to the listed level in Pool School? Across a summer that adds up a lot 2bags vs 3.5bags each time. Any risks shocking at a lower level?