Interesting...just finished reading _The Complete Walker IV_ by Fletcher & Rawlins...

It is certainly practical to distill fresh water from sea water if you have the inclination and the _fuel_.

If you are "hiking down the California coast" as he was, did you miss the fact that 1) he had hidden caches of food and water and 2) he periodically stopped at "roadside diners" and such to "tune into civilization"?!

I'm not knocking it. It's just not as Herculean as it sounds.

That being said, the safest method I've been able to find of purifying water is to boil it. Fitlers and chemicals will do if boiling is not available, but are not infallible.

And nothing will get petroleum distillates out of your groundwater except time and elevation (re: hurricane katrina, and my old unit deploying reverse osmosis water units to LA).