Below-Ground Solar Still. Materials consist of a digging stick, clear plastic sheet, container, rock, and a drinking tube.
(a) 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 should be easy to dig, and will be exposed to sunlight.
(b) Dig a bowl-shaped hole about 1 meter across and 24 inches deep.
(c) Dig a sump in the center of the hole. The sump depth and perimeter will depend on the size of the container you have to place in it. The bottom of the sump should allow the container to stand upright.
(d) Anchor the tubing to the container's bottom by forming a loose overhand knot in the tubing. Extend the unanchored end of the tubing up, over, and beyond the lip of the hole.
(e) Place the plastic sheet over the hole, covering its edges with soil to hold in place. Place a rock in the center of the plastic sheet.
(f) Lower the plastic sheet into the hole until it is about 18 inches below ground level. Make sure the cone's apex is directly over the container. Ensure the plastic does not touch the sides of the hole because the earth will absorb the moisture.
(g) Put more soil on the edges of the plastic to hold it securely and prevent the loss of moisture.
(h) Plug the tube when not in use so that moisture will not evaporate.
(i) Plants can be placed in the hole as a moisture source. If so, dig out additional soil from the sides.
(j) If polluted water is the only moisture source, dig a small trough outside the hole about 10 inches from the still's lip. Dig the trough about 10 inches deep and 3 inches wide. Pour the polluted water in the trough. Ensure you do not spill any polluted water around the rim of the hole where the plastic touches the soil. The trough holds the polluted water and the soil filters it as the still draws it. This process works well when the only water source is salt water.
Transpiration Bags. The mechanism a transpiration bag employs to source/collect water is the same as the solar still. That is why they are also known as “Above-Ground Solar Stills”. This device allows the survivor to make water from vegetation. To make the above ground solar still, locate a sunny slope on which to place the still, a clear plastic bag, green leafy vegetation, and a small rock.
(a) Fill the bag with air by turning the opening into the breeze or by "scooping" air into the bag.
(b) Fill the bag half to three-quarters full of green leafy vegetation. Be sure to remove all hard sticks or sharp spines that might puncture the bag.
CAUTION Do not use poisonous vegetation. It will provide poisonous liquid.
(c) Place a small rock or similar item in the bag.
(d) Close the bag and tie the mouth securely as close to the end of the bag as possible to keep the maximum amount of air space. If you have a small piece of tubing, small straw, or hollow reed, insert one end in the mouth of the bag before tying it securely. Tie off or plug the tubing so that air will not escape. This tubing will allow you to drain out condensed water without untying the bag.
(e) Place the bag, mouth downhill, on a slope in full sunlight. Position the mouth of the bag slightly higher than the low point in the bag. The bag can also be wrapped around leaves still on a tree as show in the video below
(f) Settle the bag in place so that the rock works itself into the low point in the bag.
(g) To get the condensed water from the still, loosen the tie and tip the bag so that the collected water will drain out. Retie the mouth and reposition the still to allow further condensation.
(h) Change vegetation in the bag after extracting most of the water from it.
(i) Using 1 gallon zip-loc bag instead of trash bags is a more efficient means of construction.