Kathy James - Building A Solar Water Still

The Solar Still functions under the general principle of the "greenhouse effect." Solar energy heats the ground by passing through a clear plastic barrier. Moisture from the soil then evaporates, rises and condenses on the underside of the plastic barrier above.

Materials

There are only 2 essential components to constructing the Solar Still -- a small container to catch the water and a 6 x 6-foot sheet of clear plastic.

The sheet of clear plastic can be a thin painting drop cloth as long as there are no tears or holes.

A 6-foot length of flexible plastic tubing, similar to the kind used in fish tanks is a non-essential but desirable addition to the still components. This will allow you to drink accumulated water without needing to break down the solar still, inevitably affecting its efficiency.

Construction

The best part of this life-saving device is that for something that collects water from seemingly nothing, the solar still is amazingly simple to build. Here's how:

1. Dig a pit approximately 4 feet wide and 3 feet deep.
2. In the center of the pit, dig another small hole deep enough for the small water container.
3. Place the container inside, then run the tubing from the container to the outside of the pit. If there is tape available, tape the tubing to the inside of the container.
4. Blanket the pit with the plastic sheet, evenly on all sides, but not touching the bottom of the pit. Anchor the corners with boards, bricks or rocks.
5. Find a small rounded rock to place in the center of the sheet, over the water container. This will keep the plastic centered and control any flapping from the wind. Gently push down on the center weight until the sides slope to a 45º angle. If the pit is dug deep enough, this should leave the center weight just a few inches above the water container.
6. Next, secure the edges of the plastic sheet with boards, bricks, or rocks and dirt. Make sure there are no places where moisture can escape.
7. Close the tubing end with a knot, or double it back and tie it closed with a twist-tie.

Within 2 hours, the air inside the still will become saturated with moisture and begin to condense onto the underside of the plastic sheeting. Because of the angle of the plastic, water will run down towards the center. Finally, drops will gather and fall from the apex down into the water container. As the container fills, simply sip fresh, sterile water from the plastic tubing. In especially dry conditions, water output can be increased by placing succulent plant material inside the still.

The Solar Still only takes about an hour to build. If constructed correctly, it can yield about a quart of water a day.

Another method of collecting water is to wrap a larger clear plastic bag onto the end of a leafy tree branch and tie the end shut around the branch. The leaves will aid in the condensing process.
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