4 hours is a worst case scenario. It depends upon water temperature. See the chart here for an idea of the various wait times.

Lori posted the link of the chart and the four hours is indeed a "worst case scenario". I also combine this with the Frontier Pro when the water is suspect, so I never have to wait more than 30minutes.

Well, I use the canadian version, which is called "pristine" but it's the same stuff. and the label I read says it kills stuff just fine.

And yes that means I typically wait 30 minutes. Most of my friends who pump wait more than 30 minutes of pumping and fiddling and filter breakage and blah blah..

I hit water source, suck back what's in the bag, fill up, treat, and keep walking. (or chill for 30 minutes and watch the pump follies if I am with one of those)

Does the label for the Canadian stuff mention protozoa (giardia, crypto)? The US version does not, because (1) the dosage is insufficient and (2) the exposure time is insufficient unless the water is clear and warm. In other words, Aquamira will kill bacteria and viruses but not the creatures whose proliferation started us all treating our water in the first place!