Quote Originally Posted by pratzert View Post
Chlorine DOES have a shelf life.

So it may make sense that a pool stores Bleach "may" be "Fresher" since they would likely have a quicker turnover of their stock.
Most pool stores that sell chlorine in reusable carboys usually have an on site storage tank for the chlorine and fill the carboys themselves (It was a job I really hated! Ruined more work clothes and shoes that way filling a hundred carboys in the hot Florida sun! We got chlorine deliveries weekly (by a large tanker truck) and had two storage tanks out back. I'm talking about tanks standing 15 feet high and about 5 feet across! We sold a LOT of liquid chlorine. The chemical company we got it from guaranteed 12.5% but it was closer to 16-17% when delivered.
The gallon jugs of 10% from such companies as HTH (we sold those also) are often stored n warehouses and on site for long periods before they get sold so they often are not very fresh. The same goes for bleach from most discount and grocery stores. (Walmart might be the one exception to this. They seem to run out of bleach and need to restock it on a very regular basis, in least in my area.)