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Ultra Violet (Solar) Water Purification

Updated on February 20, 2014

Water is one of the most fundamental building blocks for life. Our bodies are made up of about 60% water and we can not survive for more than a couple days without water. In developed countries we often take safe, clean drinking water for granted, but anyone that has traveled to, or lived in a third world country will know that you can't always count on the water from a faucet to be safe.

An inexpensive, easy method of water purification could reduce disease and save thousands, if not millions of lives in the third world. Even if you have safe drinking water available in your home, knowing how to purify your water in the event of a disaster, or survival situation could be of great value. In the wake of hurricane Katrina, thousands of residents of the southern U.S. were left with unsafe drinking water.

Enter SODIS (Solar Water Disinfection), SODIS is an effective method for purifying water using only empty water bottles and sunlight to make safe drinking water. SODIS makes potable drinking water available to individuals that have limited resources.

Checking the clarity of the water
Checking the clarity of the water | Source

How It Works

The SODIS water purification uses one of the most abundant, free resources in the world, sun light. More specifically, the UV (ultra violet) rays that are emitted from the sun. Anyone that has looked into smaller UV water purification systems, primarily those used by hikers and backpackers, will know that small, battery powered devices are becoming popular for sterilizing water on the hiking trail.

The disadvantage of the hand held devices is that the rapidly deplete batteries, can treat a relatively small amount of water per treatment, and they are expensive. In comparison the SODIS method only requires direct sunlight and a water bottle, or as many water bottles as you can get your hands on to treat large amounts of water.

Boiling is also a very popular method for treating unsafe water. Boiling is one of the most effective method for killing harmful biological impurities in water. The disadvantage with boiling is that it requires a method for heating the water, whether it is a stove or simply firewood. While this method is very convenient at a home, it can be prohibitive in more primitive locations where a stove is not available, or in parts of the world where firewood is hard to come by.


What is the difference between PET and PVC? PVC stands for PolyVinyl Chloride, plastics made from PVC will break down over time, particularly under UV light, the very light that makes SODIS work. The PVC can also leach chemicals into whatever is in contact with it, making it unsuitable for use around food products.

PET stands for PlyEthylene Terephthalate. PET plastics are made to resist UV rays, won't leak chemicals into foods or liquids and are more easily recycled than PVC plastics.

When using a water bottle for the SODIS method, make sure that the bottle indicates that it is made out of PET plastics.

How To Purify Your Water

To get started with the SODIS method, find a clear, label-less PET water bottle. You want it to not only be clear, but free from excessive scratches to allow maximum light transmission. The next step is to fill the water bottle from your water source. It is best to use water that is as clear as possible. If necessary, use a piece of fabric or coffee filter to remove debris.

To test if your water is clear enough for the SODIS method to work, take a piece of newspaper and place it on a table or flat surface. Next, place your full water bottle over the title of an article. If you can look down through the open bottle and read the newsprint through the bottom of the bottle, the water is clear enough to use.

Now that you have your water ready, find a place that will be in the sun throughout the whole day. To improve the method, place your bottle on a surface that is either reflective (to bounce the UV rays back), or a surface that is dark (to increase the temperature). Not only will the UV rays purify the water, but the warmer the water gets, the faster the process works.

Make sure you leave the water in direct sunlight for at least 6 hours. If the sun isn't shining all day and you have intermittent sun, make sure you leave the bottle out for at least two days.

It's best to use bottles that hold less than 3 liters, which will allow the UV rays to penetrate the entire bottle.

SODIS And The Future

As you can see, the SODIS method for purifying water is very simple and very inexpensive. It opens up the doors of safe drinking water to parts of the world that could never before afford clean water. It is also an inexpensive method for use in the case of an emergency, where local water supplies might be contaminated or equipment is not available to filter water.

As a note, this method does not work with chemicals or metals that may be in the water. If you believe that there are chemicals in the water, find another source of water, or use another, proven method for purifying the water. This method does kill all harmful biological impurities in the water.

What method do you usually use for purifying water? Let me know in the comment section below.

September is National Preparedness Month, check out the link to see how you can prepare your family in case of a natural disaster. Make sure you include some water bottle so that you can purify your water using the above method!

If you want to read some of my outdoor related writing, check out my blog:


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    • Adventure Colorad profile image

      Adventure Colorad 6 years ago from Denver,CO

      I'm glad you enjoyed it CW, it's a great resource that's available to people that don't have more expensive resources available.

    • CWanamaker profile image

      CWanamaker 6 years ago from Arizona

      It's so simple that I'm hitting myself in the head for not thinking of it! I have seen and worked on UV disinfection units before, but it never occurred to me that there was enough radiation coming from the sun to accomplish the same thing. Thanks for turning me on to such a simple yet impressively effective idea.

    • Adventure Colorad profile image

      Adventure Colorad 6 years ago from Denver,CO

      Thanks for the link Monica, I had actually used that to double check some of my facts.

    • profile image

      Monica 6 years ago


      Check out this:

      This is the official website of the guys who invented the method.