When you say "he added enough bleach to get up to x amount"....are you testing it at that level, or just assuming it's there because that's what the bleach calc says? If you're testing it at the higher level and then testing it at the lower level, then you still have a problem with your water. If you're just assuming that it's hitting the high level you think it is, then you probably don't have nearly the chlorine demand that it appears. With the weaker concentration, it's not going as high as you think, and it's probably not going high enough to maintain a shock level for very long. When you make your next addition, give it an hour or so after the addition to circulate, and then test it to see what you get. That result will make the results from the next test meaningful....make sense?

AS far as buying fresh bleach--there's really no way to know--you could ask the manager of the place where you are buying it how long that particular lot has sat around, but even he can't control things like how long it sat in the warehouse, what the temps were, the storage conditions, etc. I buy mine at WalMart, where there's a HUGE turnover--they completely turn over their bleach (generic, anyway) shelves at least every couple of days.

Janet