Who knew? Not me, until recently. That aging bottle of unopened bleach that I stored next to my water containers five years ago? Probably useless.

Clorox says the shelf life is about a year, and that bleach breaks down into salt and water over time.

Suspicious fellow that I am, it crossed my mind to wonder if this was just a ploy to sell more bleach.

But here's another source, from a person in Environmental Health & Safety at the Scripps Research Institute, that says the same thing (and also includes some interesting info about diluting bleach):

Everything You Always Wanted to Know About Bleach But Were Afraid to Ask

So now I know if I want to stash away bleach for disinfecting water (or anything else), I should get a new bottle every year.