Joe,

Sounds like you have the same thing. I bought mine from Nashbar for five dollare each on sale.

In Utah, I imagine that you would have to be wetting them all the time because of the dry air, but the faster the evaporation, the more heat lost.

I can't explain our different results, but I do notice that the Gatorade is much cooler than the water.

OK, here is a thought. when I start with cooler water (morning, etc.), the bottles will stay cool all day if kept damp. If I refill the bottles mid day from the blatter, they take quite a while to have a noticable difference in temp.