SODIS Method: How to purify water with sunlight

How to purify water with sunlight: If you ever find yourself in a survival situation in desperate need of safe drinking water, the SODIS Method could literally be a lifesaver. Learn how to purify water with sunlight. All you need to use the SODIS Method is clear plastic bottles and sunlight.

What is SODIS?

SODIS is short for “Solar Water Disinfection.” This method is simple and easy. All you need is a clear plastic water bottle and natural sunlight. SODIS is a free and decentralized water treatment that is usually applied at the household level. It is recommended by the World Health Organization. The SODIS method uses a combination of UV light and increased temperature (solar thermal) for disinfecting water using only sunlight and repurposed PET plastic bottles.

How does SODIS work?

SODIS is a portable method of water purification that harnesses the UV rays in natural sunlight and utilizes them to destroy harmful bacteria, viruses, and parasites that may be present in your drinking water. Isn’t it amazing that you can put questionable water into a clean and clear plastic bottle, expose it to direct sunlight for the proper amount of time, then render it safe to drink?

FYI: Water that is contaminated with non-biological agents such as toxic chemicals or heavy metals requires different purification steps.

Harmful contaminants that are destroyed by 6 hours of sun exposure:

  • E. Coli
  • Vibrio Cholera
  • Salmonella
  • Shigella Flexneri
  • Campylobacteria jejuni
  • Yersinia enterocolitica


  • Rotavirus


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

Cheap water purification using SODIS

Is the SODIS method safe?

A common concern is whether toxins from the plastic bottle will leach into the water when the SODIS method is being performed.

This method was tested by the Swiss Federal Laboratories for Materials Testing and Research and they discovered that the toxins that are emitted from the bottles are extremely low (according to the standard set by the World Health Organization.)

WHO, Red Cross, and UNICEF referred to SODIS 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.

Portable UV Water Purifier | SteriPen

UV light is so effective at destroying micro-organisms that outdoor gear companies have started to take notice and capitalize on it. When I don’t have the time to wait for the sun to purify my water, I use this SteriPen. It shines a powerful UV light into your water and can render 1 liter of water safe to drink within 90 seconds. This is the quickest and easiest way to purify water with UV light.

How to use the SteriPen and why I switched

SODIS Method Supply List:

A clear, plastic bottle

  • Your bottles should be plastic rather than glass because they will not break easily due to temperature changes or heat exposure. Also, plastic bottles are easy to find all around the world.
  • Use clear PET (Polyethylene Terephthalate) plastic bottle
  • The recycle code at the bottom of the bottle should be Recycle Code #1 (A recycling symbol with the number 1 inside). 
  • The bottle should be smaller than 2 liters
  • Use a bottle that is in good condition and free of scratches or visible signs of wear


  • Make sure that you water is visibly clear, clean, and odorless
  • Use the very best source of water possible. A running source such as a river or creek is ideal
  • Do your best to ensure that the water isn’t polluted with chemicals (avoid acquiring water from sources near industrial areas, sewers, or latrines)

Filtering Cloth

  • You will need something to filter out particles and impurities like leaves, rocks, or sand in the water. A bandana or a shirt will work.

Natural Sunlight

  • This method requires natural sunlight. Avoid shady, dark forests or thickets. Meadows and wide open spaces are ideal.

Reflective Surface (optional)

  • Bottles will heat faster and hotter if they are placed on a sloped sun-facing reflective surface
  • A corrugated metal roof (opposed to thatched roof) or slightly curved sheet of aluminum foil will increase the light inside the bottle
  • A mirror, metals, glass or even white surface (such as a poster board or box) can improve your sun exposure

Salt (optional)

  • Take it easy with the salt because you don’t want to accidently dehydrate yourself
  • Adding salt to murky water gets the particles to stick together and settle at the bottom of the bottle. This makes the water clearer for better sanitation.

Lime Juice (optional)

  • It’s less likely that you will have limes lying around, but if you do, you’re in luck!
  • Lime juice can help cut down the purification time from 6 hours to 30 minutes! Thanks to chemical compounds called psoralens, that are present in lime juice and shown to kill pathogens in both blood and water. 
  • Did you know that lime juice has been known to kill malaria and other bacteria?

SODIS Method Instructions:

Step 1- Sanitize the bottle

Make sure that the bottle is clean and free of dirt and dust. Remove the label from the bottle. This will allow the sunlight to quickly infiltrate the water and get to work on destroying the harmful contaminants.

Step 2- Find out of the water is “turbid”

Check to see if the water is cloudy, murky, opaque, or thick with suspended matter. To test this, fill the bottle with water and put it on top of a newspaper headline. Now look down into the bottle and try to read the headline. If the water is to turbid to read the headline, you will need to filter it with the cloth or add some salt.

Step 3- Fill, Cap, Shake!

Fill the bottle with water 75%. Now screw the top on securely and shake the bottle for a minimum of 30 seconds. This adds oxygen to the water which will help to kill germs and improve the taste.

Step 4- Fill additional bottles with water

This is a good time to add lime juice to the bottles. Even if you are just filtering water for yourself, filter as much as you can. This method is dependent on the weather and you don’t know exactly when you’ll have another sunny day. You don’t want to wake up dehydrated in the middle of the night with no water to drink. This filtering process takes some time so plan ahead!

Step 5- Place the bottles in direct sunlight

It is important to lay the bottles on their sides rather than upright. This allows more UV rays to penetrate the water. If you have reflective surfaces, this is the time to use them. A mirror is the best option, but you can also use white cardboard, shiny tin (a metal roof), or white tree bark will even help reflect more light into the bottles.

Step 6- Wait and let the magic happen

If it’s a sunny day leave the bottles in the direct sunlight for 6 hours. If it’s a cloudy day then this process could take up to 2 full days. The temperature doesn’t matter. It is the UV light that you are trying to capture and use. Not the heat. If it is so cloudy that it rains, collect that water and drink that instead. Either way you’ll have clean water to drink!

Drink up and enjoy!

Congratulations! You now have safe, drinkable water! Enjoy it and repeat these steps when necessary. You can drink the water directly from the bottle or pour it into another container. Make sure that you keep the cap on because you don’t want it to spill, get contaminated, or evaporate.

SODIS Method: How to purify water with sunlight


This method is easy and cost-effective which makes it one of the best methods for purifying water in a survival situation. Once you learn this skill, you can take it with you everywhere you go and have an easy way to access clean, drinkable water.

For more water purification methods visit read my article “The 5 Best Methods of Purifying Water for Survival.”

Thank you so much for joining me again! Have you ever tried the SODIS method? Comment below to share your tips and tricks!

See you soon!