Wow Jim! Thats 40lbs of water (plus the container weight).

I live in the Sonoran desert and 7-8mos of the year its 85'F + almost everyday. Wanting the ability to haul enough water for several days is actually a reason I keep thinking I need one of these:
Cabela's Outfitter Pack Frame

5gals is just enough water for a 4 day hike. Two days out & two days back plus 1 gal spare for emergency.

But really, when it's 95'F +, and I'm being very physical, 1 gal/day is waaaaaay insufficient. When it's 110+ I can step outside, and be busy in the sun for 5 min. and start feeling dehydrated. I'm not sure 1 gal/day is enough for anything but slower dehydration when it's truly hot.

I've felt a 120'F day here one time back in the 90's and I purposefully stayed outside with the sun at high noon for 30 minutes or so just to feel it.
When I angled my head to let the sun shine through my ears they hurt.
I blew my breath on my hands and the 98.6'F air felt nice and cool.
I could feel my skin sunburning, in just a few minutes.
Heat like that is dangerous to be in, but people do it.

I have sympathy for the guys in Iraq where they are facing 120'F + everyday.

If anyone on the board is backpacking lots of water how are you doing it?