SODIS Method: Using Plastic Bottles and the Sun to Purify Water

The Sodis Method Title

If you’re ever in a survival situation where you need safe water to drink, the SODIS method could literally be a lifesaver.  Using just a simple plastic bottle and the sun, you can have clean drinking water available within hours. This method can be used to get drinkable water from lakes, rivers, or other sources anywhere in the world.

What is SODIS?

SODIS is short for “Solar Disinfection” which is a method of purifying water for drinking using only a clear plastic water bottle and natural sunlight.

How does SODIS Work? 

Sodis harnesses the UV rays in natural sunlight and uses them to kill harmful bacteria, viruses, and parasites that may be present in your drinking water. By placing questionable water in a clear plastic bottle and exposing it to direct sunlight for the proper amount of time, you can render it biologically safe to drink.

When harnessed correctly, The UV rays from the sun will target and kill living biological contaminates, such as bacteria, parasites, protozoa, worms, and viruses. Amazingly, properly performed, this method for purify water can kill a whopping 99 percent of all biological contaminates!

Types of harmful contaminants that will be killed after 6 hours of exposure to the sun:


  • Escherichia coli
  • Vibrio Cholera
  • Salmonella
  • Shigella flexneri
  • Campylobacteria jejuni
  • Yersinia enterocolitica


  • Rotavirus


  • Giardia
  • Cryptosporidium (this needs an exposure of 10 hours to terminate)


Is the SODIS Method Safe?

Others have mentioned concerns that some toxins might be leaching from the plastics into the water when the SODIS process is being performed.

The Swiss Federal Laboratories For Materials Testing and Research have tested this method and discovered that the toxins being emitted from the bottles are in extremely low levels, according to the set standard by the World Health Organization (WHO).

Apart from WHO, international bodies like the Red Cross and the United Nations International Children’s Emergency Fund have given this method recognition and credibility for its ability to kill germs in water.

SteriPen – Portable UV Water Purifier

Ultra-violet light is so effective at killing micro-organisms that even certain outdoor companies are starting to take notice. When I don’t have time to wait a few hours for the sun to purify my water, I use this SteriPen. This will shine a bright UV light into your water and can render 1 liter of water safe to drink in 90 seconds. This is certainly the quickest way to use UV light to sterilize water for drinking.

See Price on Amazon

This method was also given the Red Cross Prize in 2006. Additionally, WHO and UNICEF termed it as ‘User-friendly, Cost effective, and a measure of The Proven Health Impact.

In addition to killing biological-contaminants, the SODIS method is known for its ability to prevent diarrhea, which is a leading cause of death in developing countries.

SODIS Water Purification in Indonesia
Here’s a group of people using the SODIS method in Indonesia. Notice how the bottles are clean, stickerless, and laying on their sides for optimal UV penetration.

What You’ll Need for the SODIS Method

A Bottle

  • The bottles should be plastic, not glass. Plastic bottles are recommended because they will not easily break due to temperature changes/exposure to heat. Additionally, plastic bottles are incredibly easy to find all over the world.
  • Use a PolyEthylene Terephthalate bottle, for short, most people just refer to them as “PET”.
  • Make sure the recycle code at the bottom of the bottle reads Recycle Code #1 (A recycling symbol with the number 1 inside). 
  • The bottle should be no larger than 2 liters.
  • The bottle should be in good condition, without any scratches or visible signs of wear. Don’t mind the bluish tinge that most bottles have, this method will still work.


  • The water should visibly appear clean, clear, and odorless.
  • Use the best source the water possible. A running source, such as a creek, or river is best.
  • Do your best to ensure the water is not chemically polluted (don’t source your water from nearby any industrial areas, sewers, or latrines).

A Filtering Cloth

  • You’ll need something to filter out the visible impurities in the water, such as bits of leaves, sand, or tiny rocks. A shirt or bandanas will do.


  • Getting to a well-lit area is important, don’t try the SODIS method in your bat cave or a thicket in the forest. Meadows and wide open spaces are most ideal.

A Reflective Surface (OPTIONAL)

  • A mirror, metals, glass, or even a white background (like a posterboard) can be useful for further exposing your water bottle to the sun. This will mean quicker and more powerful results.


  • Take it easy with the salt, you don’t want to accidentally dehydrate yourself with it.
  • When salt is added to murky water, it gets the particles to better stick together and settles at the bottom of the bottle. This makes the water clearer for better sanitation.

Lime Juice (OPTIONAL)

  • I know, I know, chances are you won’t have any lime juice laying around. If you do though, you’re in luck!
  • Lime Juice helps to cut down the time needed to disinfect the water from six hours to just thirty minutes! This is because of chemical compounds called psoralens, that are present in lime juice and shown to kill pathogens in both blood and water. 
  • Lime juice has also been known to kill malaria and other bacteria.
SODIS water purification, be sure to use a #1 plastic bottle
Check for this symbol on the bottom of the water bottle. 1 is the only number you should be seeing.


Step 1- Clean the Bottle

Remove the wrap/sticker from the bottle; this allows sunlight to more quickly infiltrate the water, and get to work killing those harmful contaminants. Make sure the bottle is clean and free from any dirt or dust.

Step 2 – See If the Water Is ‘Turbid’

Basically, you’re just checking to see if the water is cloudy, murky, opaque, or thick with suspended matter. To easily test this, fill the bottle with water, and place it upon a newspaper headline. While keeping your prankster friends back, look down into the bottle, and try to read the headline. If the water is too turbid to do so, you need to filter it with a filtering cloth or add a pinch of salt.

Step 3 – Fill, Cap, and Shake

Fill the bottle to only about 75% full with water. Then securely screw on the cap and rapidly shake the bottle for a minimum of 30 seconds. This adds oxygen to the water, which will further help to kill germs and improve the taste.

Step 4 – Fill Additional Bottles with Water

Add in any lime juice to the bottles if you have it. Even if you are filtering water just for yourself, filter as much water as possible. You don’t know when you’ll have another sunny day, and you don’t want to wake up in the middle of the night feeling dehydrated with nothing to drink. The filtering process takes some time, so do your best to plan ahead.

Step 5 – Place the Bottles in Direct Sunlight with as Much Reflection as Possible

Lay the bottles on their sides, and not upright. This allows more UV rays to penetrate the water. If you have reflective surfaces, now is the time to use them. Though mirrors are most ideal, white poster boards, shiny tin (such as roof metal), or even white tree bark will help reflect more light into the bottles.

Step 6 – Wait

If it’s a sunny day, wait 6 hours. If the weather is more cloudy, this process could take up to two full days. The temperature doesn’t matter, it’s just the UV light you’re trying to capture and use, not the heat. If it is so cloudy that is starts to rain, collect that water to drink instead. Either way you’ll have drinkable water!


You now have safe, drinkable water. Enjoy it, and repeat these steps as needed. When you drink the water, you can drink directly from the bottle, or pour the water into another clean container. Don’t let it sit idle without a cap however, as it could be spilled, re-contaminated, or even evaporate.

Basics of the SODIS method. Step-by-step.
The SODIS method can be better understood by this simplified step-by-step graphic.


With its simplicity, cost-effectiveness, credibility, and little energy needed from your end, it is safe to say that this is one of the best methods for purifying water to drink in an emergency situation. Once you learn this skill you can take it with you to just about anywhere on the planet so you’ll always have safe water to drink.

Looking for other ways to purify your water? Check out this article written by John himself.

Have you ever tried the SODIS method? What are your tips and tricks? Share those in the comments below.

John Walter

John Walter is an emergency preparedness consultant with eight years of experience and training in related fields. He is a passionate prepper living in the Sacramento area of California.

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