An article at offers tips on finding safe water sources that need no filters.

One day on a mountain hike in hot weather I ran completely out of water. As the day wore on I realized it was going to be a long, thirsty hike back to base camp before I could get any clean water. Eventually thirst drove to me to consider a drink of raw water, and I started scouting for a likely source. I finally drank from a fast-moving streamlet on a steep slope that carried snowmelt down to the valley stream below. The water was icy cold and very clear. At that point I was so thirsty I didn’t really care what happened, but I noticed after a few days that everything was fine.

The story points out what many backcountry travelers already know: unpolluted water is perfectly safe to drink; the trick is to identify potential sources of pollution and weigh the odds of pollution before you decide to filter. The condensed version:

Doc’s Rules for Sipping the Waters

  1. Study the watershed you are in. Know what is there.
  2. Look for water near to its source.
  3. Try to take water from the sideslope streamlets.
  4. Avoid water from the main valley stream.
  5. Look for icy cold water.
  6. Look for fast-moving water.
  7. Study the area for the presence of large animals.
  8. Ascertain whether numbers of elk have recently been in the area.
  9. Avoid waters near beaver ponds or cattle grazing.
  10. When possible drink a test amount before drinking liberally a few days later from those same waters.

Of course if your brain already suffers from information overload, you could save a lot of trouble and just carry a filter along. I haven’t been in a car wreck in 15 years but I still buy insurance.

Then again, there are apt to be times when you find yourself out of water with no way to purify any water you might find. Knowing how to find clean water is insurance, too.