I read in some threads that pool store shock is not recommend by the people on this forum. The shock at my pool store is 12.5% Sodium Hypochlorite. Another pool store sells 10.0% Sod. Hyp. The chemical company down the street sells "fresh pool chlorine" and its 12.5% Sod. Hyp. The grocery store sells bleach that is 8.5% Sod. Hyp. Other than price and concentration, what's the difference?
The chemical company has the best price. I didn't calculate the grocery store price on a =% basis, but they don't have enough on the shelf to make it worthwhile.