How to Make a Solar Water Survival Still

Water is Key to Survival

In a survival situation we are often quick to find that water is the limiting factor for how long we can survive. Having enough clean drinking water, free of chemical and biological contamination can mean the difference between life and death.

In a previous Survival Topic we discussed the importance of water discipline and always staying as hydrated as possible. Without an adequate intake of fresh water to replace water lost through bodily processes, the efficiency of the survivor decreases rapidly to the point where unconsciousness or death may occur.

There are a number of ways to produce potable water that the Survival Expert should know. Where there is plenty of water and fuel available usually one of the best ways to make water safe to drink is by bringing it to a boil. A very popular article on Survival Topics broke the news that you do NOT have to waste fuel boiling water for X number of minutes as many so called health experts claim – once water hits its boiling point the water is safe to drink).

Damp Earth

But there are occasions when there seems to be no water available, or it is brackish (part salt water), or thick with vegetation and therefore seemingly undrinkable. However, if there is an abundance of sun and you have your survival kit with you, all is not lost. You can make a solar still.

Solar Still Essential Items

While walking in the hot sun along a dry stream bed I found a low spot where water was likely to accumulate. It is a little known fact that often there is as much water flowing underneath the stream bed as there was flowing on top during non-drought periods. This water is slowly percolating between the interstitial voids of the stream bed and is generally out of sight except where pools form due to bedrock or clay barriers.

Solar Still Plastic

Sometimes you can tap into this underground source of water by simply digging a hole and allowing it fill with water. On other occasions the material will only be damp and there is no water that you can simply scoop up for a refreshing drink.

As you can see in the picture by digging down into the gravel a short way I found the pebbles to be damp with a light coating of moisture that makes them look darker than the dry stuff on top. Although there is no water to be directly obtained here, this is an ideal environment for making a solar still because there is

damp ground
hot sun
and I have a clear plastic sheet

Plastic for a Solar Still

In my survival kit I always carry a couple of 50-gallon drum liners. These large garbage bags have a myriad number of uses, from improvised sleeping bags and shelters to rain gear and, in this case, solar stills. I recommend always having some on hand.

Solar Still Hole

Since I needed a flat sheet of clear plastic in which to make the solar still, I slit the drum liner open using the blade of a multi-tool. To make a handy cutting board for this purpose I found a piece of driftwood which I inserted into the bag. Then it was an easy matter to slice the drum liner open using the blade of the multi-tool. This produced a sheet of plastic about 5ft wide by 6ft long.

The Solar Still Hole

Next I dug a hole into the damp gravel about 3-ft deep and 4ft in diameter. This can be difficult work, especially in the hot sun. I happened to have a folding army shovel as a digging tool, but you can use a stick, your hands, or your mess kit to dig with.

Solar Water Still

Once the hole is dug, place an empty container in the middle of the hole and then cover the hole with your clear plastic sheet. Place stones or piles of earth on the outer edge of the plastic to hold it in place.

Take a small roundish pebble and place it in the middle of the plastic, pushing the plastic downward at this point so that its apex is directly over the empty container. Try to make the angle of the plastic from the edge of the hole to the center about 45-degrees.

Once the center stone is in place, cover the entire outer edge of the plastic sheet with material so that the seal is air tight. It is important that you make a good tight seal so that the evaporating water does not escape.

Solar Still Water

You now have a operating solar still for collecting drinkable water from the earth itself.

How the Solar Still Works

Within a short time you will notice the clear plastic sheet is cloudy with tiny droplets of water. The plastic covering has turned the damp hole into a sort of greenhouse, trapping the rays of the sun to produce heat. As the moisture within the hole evaporates, it condenses on underside of the plastic sheet and then runs down, drop by drop, into the container.

Solar Still Improvements

A larger hole and damper soil can produce more fresh drinking water but of course this is limited by the size of the plastic sheet you have on hand. You can also place juicy green vegetation inside the hole, including leaves and green grass. The heat will draw the water from these materials.

Brackish, sea water, or vegetation stained water, urine, or any other undrinkable water source may also be used to increase the water output of your solar still. The process of evaporation will separate the fresh water from all biological pollutants and some chemical pollutants as well.

Solar Still Cautions

This brings up an important point – the solar still may be used to distill fresh water from chemically polluted water as long as the contaminants do not condense with the water onto the plastic sheet. This is why urine can be turned to fresh water, as the various salts and ammonia etc are left behind as the water evaporates. However liquids such as radiator fluid should not be added to a solar still since some of the toxins may vaporize and condense along with the water.