Watch the date codes also, bleach looses strength as it ages, and is best kept in a cool dark place so it will stay fresh longer. The date code is usually in the format of YY DAY OF YEAR - PLANT CODE so bleach I might buy here in Louisiana may say 16 187 TX1 for 187th day of 2016 packaged for plant 1 in Texas. (Today is the 240th day of the year, so bleach packed on 187th day of the year is about 2 months old, I used the bleach bottle in my laundry room for the example, so it gets a bit less turnover than the bleach for the pool).