StoSoutdoors

   If you can find the source of water in the mountains or hills, where it actually bubbles out of the ground, you are usually safe in drinking it. If you are downstream from other animals and humans, it is best to boil water for 10-20 minutes or distill it. As a last case option, 2% iodine solution can be used. Add five drops to a quart of clear water or 10 drops to dirty water.
  The fact that natives may assert a water source is pure could indicate they have built up a degree of immunity. To their systems, the water is not tainted (polluted). Even the loneliest wild stream can be infected with Tularemia (commonly called rabbit fever) by wild animals such as muskrats and beavers. Tularemia can also be carried by meadow mice, ground hogs (woodchucks), ground squirrels, tree squirrels, beavers, coyotes, opossums, sheep, and various game birds
Polluted water can be sterilized by adding hot stones to the water in the filter. The water will soon boil becoming sterile and safe drink.
In areas where there is the likelihood of water being unsanitary (near cities or villages), it is always safer to boil before drinking or add a pinch of chloride of lime.
Water which is very muddy, dirty or stagnant can be clarified through a good filter made from a pair of drill trousers with one leg turned inside out and put inside the other leg.
The cuff is tied and the upper part held open by 3 stakes driven well into the ground. Fill with the dirty water and then drop in the hot stones.
  The water will filter through and MUST be caught by a container and poured pack until the dirt has been filtered. Boil the water at least 10 minutes. Remember, just moistening your lips with polluted water can make you sick for days; it can even kill you.
Rainwater collected in clean containers or in plants is usually safe for drinking. However, purify water from lakes, ponds, swamps, springs, or streams, especially the water near human settlements or in the tropics.

   Dig in the stream bed at the outside of a bend. This is the part of the river or stream that flows the fastest, is less silted, deepest, and the last part to go dry.

  Select a site where you believe the soil will contain moisture (such as a dry stream bed or a low spot where rainwater has collected). The soil at this site should be easy to dig, and sunlight must hit the site most of the day.

To construct the still -

  Dig a bowl-shaped hole about 1 meter across and 60 centimeters deep.
Dig a sump in the center of the hole. The sump’s depth and perimeter will depend on the size of the container that you have to place in it. The bottom of the sump should allow the container to stand upright.
Anchor the tubing to the container’s bottom by forming a loose overhand knot in the tubing.
Place the container upright in the sump.
Extend the unanchored end of the tubing up, over, and beyond the lip of the hole.
Place the plastic sheet over the hole, covering its edges with soil to hold it in place.
Place a rock in the center of the plastic sheet.
Lower the plastic sheet into the hole until it is about 40 centimeters below ground level. It now forms an inverted cone with the rock at its apex. Make sure that the cone’s apex is directly over your container. Also make sure the plastic cone does not touch the sides of the hole because the earth will absorb the condensed water.
Put more soil on the edges of the plastic to hold it securely in place and to prevent the loss of moisture.
Plug the tube when not in use so that the moisture will not evaporate.
You can drink water without disturbing the still by using the tube as a straw.

  IODINE WATER PURIFICATION TABLETS
Chlorine-releasing compound can not be relied upon in semi-tropical and tropical areas.
Water in those regions must be sterilized either by boiling or by iodine water purification tablets containing the active ingredient Tetraglycine Hydroperiodine, These measures have been adopted as standard by the armed services of the USA.
These tablets have been proved effective against all the common water-borne bacteria. Added to water each tablet frees 8 milligrams of iodine which act as a water purification factor.
One tablet will purify one quart of water. These tablets too must be kept dry. The bottle must be recapped tightly after opening.
Step 1 Add one tablet to a quart of water in container with cap.
Step 2 Wait 3 minutes.
Step 3 Shake water thoroughly, allowing a little water to leak out and disinfect the screw threads before tightening the cap.
Step 4 Wait 10 minutes before drinking or adding beverage powders and if water is very cold, wait 20 minutes.
Step 5 If water contains decaying vegetation or is murky and discolored, use 2 tablets for every one quart.
Step 6 Make certain that the iodine disinfects any part of the container which will come in contact with your lips.