Im curious to find out if there is a way to test the strength of bleach, my local pool store sells 10.5% bleach for $3.77/jug 2.5gallon. one of the employees told me they get refills every 2-3weeks! so i am curious if its still 10.5% they do keep it in a huge tank, indoors/ac. anyway is there an easy test to check strength of chlorine? Thanks for the help

-Arron