Safety / Survival / Army Field Manuals / AFM 3-05.70
6-15. You can use stills in various areas of the world. They draw moisture from the ground and from plant material. You need certain materials to build a still, and you need time to let it collect the water. It takes about 24 hours to get 0.5 to 1 liter of water.
6-16. You can construct two types of aboveground stills. To make the vegetation bag still, you need a sunny slope on which to place the still, a clear plastic bag, green leafy vegetation, and a small rock (Figure 6-6).
Figure 6-6. Vegetation Bag Still
6-17. To make the still, you should—
6-18. To get the condensed water from the still, loosen the tie around the bag's mouth and tip the bag so that the water collected around the rock will drain out. Then retie the mouth securely and reposition the still to allow further condensation.
6-19. Change the vegetation in the bag after extracting most of the water from it. This will ensure maximum output of water.
6-20. Making a transpiration bag still is similar to the vegetation bag, only easier. Simply tie the plastic bag over a leafy tree limb with a tube inserted, and tie the mouth of the bag off tightly around the branch to form an airtight seal. Tie the end of the limb so that it hangs below the level of the mouth of the bag. The water will collect there (Figure 6-7).
Figure 6-7. Water Transpiration Bag
6-21. The same limb may be used for 3 to 5 days without causing long-term harm to the limb. It will heal itself within a few hours of removing the bag.
6-22. To make a belowground still, you need a digging tool, a container, a clear plastic sheet, a drinking tube, and a rock (Figure 6-8).
Figure 6-8. Belowground Still
6-23. Select a site where you believe the soil will contain moisture (such as a dry streambed 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.
6-24. To construct the still, you should—
6-25. You can drink water without disturbing the still by using the tube as a straw. By opening the still, you release the moist, warm air that has accumulated.
6-26. You may want to use plants in the hole as a moisture source. If so, dig out additional soil from the sides of the hole to form a slope on which to place the plants. Then proceed as above.
6-27. If polluted water is your only moisture source, dig a small trough outside the hole about 25 centimeters (10 inches) from the still's lip (Figure 6-9). Dig the trough about 25 centimeters (10 inches) deep and 8 centimeters (3 inches) wide. Pour the polluted water in the trough. Be sure you do not spill any polluted water around the rim of the hole where the plastic sheet touches the soil. The trough holds the polluted water and the soil filters it as the still draws it. The water then condenses on the plastic and drains into the container. This process works extremely well when your only water source is salt water.
Figure 6-9. Belowground Still to Get Potable Water From Polluted Water
6-28. You will need at least three stills to meet your individual daily water intake needs. In comparison to the belowground still and the water transpiration bag still, the vegetation bag produces the best yield of water.
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