A Simple Water Purification System

How to Build a Water Purification System in 10 Minutes

There’s one method of making a water still that is so simple and effective it can be done just about anywhere, constructed in minutes, and with no special knowledge or supplies. And it can turn salt water into fresh water as well.

All you need is a little sunlight to get the process going. It’s a technique that was invented by the U.S. department of agriculture to pull water from the arid Arizona deserts, and it’s even more effective in less extreme climates

How It Works

The general principle of this still is the same as the “greenhouse effect” on our planet. Heat from the sun passes through the clear plastic, heating up the soil and causing the moisture content within it to evaporate. This moisture then tries to escape into the air but gets caught on the underside of the plastic barrier and condenses into water droplets. By placing a heavy object like a rock directly over your water containment device, you will be directing the water drops to the lowest point of the plastic, where they will collect and drip into your container. After several hours, you will have perfectly clean, distilled water to drink.

This method is also effective for purifying bad water or even urine. Simply pour the tainted liquid down close to your container (but not in it). Through the process of evaporation and condensation, only pure water will collect in your cup.

Supplies You Need

To build your solar still you need a big sheet of clear plastic, a few rocks or other heavy objects, and a container to catch your water in. A hard sided container works best, but you can use just about anything (even a sandwich baggie) in a pinch.

That’s it! A shovel certainly helps the digging process but it isn’t necessary. You can keep your sheet of plastic in your bug out bag or some other handy place where it will be accessible in an emergency.

Building Your Solar Still

First, find a patch of ground that gets lots of sunlight, especially in the early morning. If you can, choose a spot with lots of vegetation or that is a dried out stream bed. These places are more likely to have water in the soil.

Next, dig a hole that is big enough to fit your water collection container. Try to make your hole as wide as the piece of plastic you have. The more surface area your plastic can cover, the bigger the area that you can pull water from. Wider holes also need to be deeper, so that there is room for the rocks to weigh down the plastic without falling right into the water container. 

You can also dig a second hole just for your container to get it down deeper.

After setting the water container in place, cover your hole with the plastic and pile dirt and rocks around the edges to weigh it down. This is crucial because your still won’t work if an edge of the plastic comes lose.

Find a small rock or similarly weighted object and position it directly over your water container. Be sure to check if the weight of the rock is pulling too much on the plastic. If so, add more rocks and dirt to the edges.

Finally, wait several hours for condensation to occur. You should start getting water within two hours, though for best results, step up your still in the evening and check it in late morning to take advantage of morning dew. You can carefully pull out your water at any point and reconstruct the still to gather more.

When built correctly, a still like this can provide you with less than a quart of water a day depending on the humidity, sunlight, temperature and altitude. It might not be enough to let you run a marathon, but it will keep you alive in a dire situation. You can build multiple stills to maximize your water gathering potential.

Words of Caution

Be careful to keep your plastic as clean as possible before building your still. Dirty plastic will produce dirty water and might make you sick if you drink it.

Also, remember that this solar still is a lifesaving device, not an alternative for packing your own water. If you are going hiking or camping, be sure to bring all the water that you need with you as well as a regular water purifier in case you run into trouble. A solar still like this should be saved for true emergencies.