Reply #88: Even better. Buy a backpackers water filter.

[Xithras]

For $60 to $75 you can buy a backpackers water filter that can make drinkable water from nearly any water source you can find. I have a Katadyn that will make about 75 gallons of fresh water from brackish standing ponds, and about 400 gallons of fresh water from reasonably clear river or lake water (the dirtier the water source, the faster the filter plugs).

I bought mine because I'm a hiker, but I've always been a bit suprised that people don't use them as an emergency water source more often.