How to Make a Solar StillJanuary 3, 2013 by Melanie Swick | 3 Comments
You can survive (unpleasantly) for up to 30 days without food, but you’ll be lucky if you can make it three days without water. As your body becomes dehydrated, you begin to get weak and tired, suffer headaches, low blood pressure, and rapid heartbeat, and eventually become delirious enough to make really bad decisions. I wish I could say this was just academic knowledge, but unfortunately a Marine on deployment did exactly that, causing his slow and painful death, alone in a barren desert.
That was one hell of a way to learn a lesson at 19 years old, and it’s stuck with me to this day; that’s why I take water almost everywhere I go. The bad news is that since water is heavy, at about 8.5 pounds per gallon, you can only carry so much and it’s eventually going to run out. The good news is that with some basic equipment, you can replenish your water supply anywhere by making a simple solar still.
To get started, you’ll need a sheet of plastic (I keep a roll of 25′ x 10′ plastic drop cloth in my BOB), a hollow plastic tube, and a collection container. A shovel helps, but if you don’t have one, you can use a flat rock or even your hands to dig a hole. Larger is better, but your plastic sheet will need to cover the entire hole with a slight overlap. Place your collection container in the center of the hole, surrounded by green vegetation. You can also pour unpurified water or salt water into the hole, being careful not to spill any into your container. Put one end of your plastic tube into your container and the other end outside of the hole, then lay your plastic sheet loosely over the hole and cover the edges with dirt, forming an airtight seal. Finally, place a small rock or handful of sand in the center of the plastic sheet to form an inverted cone.
As the sun’s heat increases the temperature inside the still, the unpurified water or salt water, and/or moisture from the green vegetation will vaporize, leaving behind any impurities, and rise until it hits the plastic sheet, where it will collect and drip down to the center, falling into your collection container. At this point, you can drink from the plastic tube. Keep in mind that the volume of water produced will depend on the temperature and what you put into the hole, so you may need to make several stills to produce enough water to stay hydrated. Also, it’s not a bad idea to tie or block off the end of the tube to prevent any evaporation, though it would be minimal.
It’s simple, cheap, and hardly adds any weight to your BOB.