HTH Super chlorine granules-Shock

[Jim Perry]

Previous owner left us a 2 lb. bottle of hth super chlorinating granules. These are 54% chlorine. Just filled the tub for the first time. Need to shock the 200 gallon hot tub. What quantity is needed, and how does one measure that quantity, please?

[chem geek]

What brand is it?  It isn't HTH is it?  If it's HTH, then that's Cal-Hypo and you shouldn't be using that in your spa unless you start with low CH and use this product instead of bleach and keep track of how much you add because for every 10 ppm Free Chlorine (FC) added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.