How to Sterilize Water With Sunlight

Every grown up human being needs about two litres of drinking water each day. It is very important to have pure drinking water. Otherwise you can suffer from diarrhea or even worse diseases. This article shows you how to sterilize water at no cost.[1]


  1. Image titled Sterilize Water With Sunlight Step 1
    Clean the bottle. Remove anything in the bottle like dirt and on the bottle like a label. This method works with PET bottles (the clear/uncolored plastic bottles often used for mineral water or soft drinks and soda) and certain kinds of glass bottles.[2]
    • The use of PET bottles for this process has been researched and found to be safe when used correctly.[3]
    • Because not all types of glass allow for the transmission of UV rays, PET is often recommended over glass, especially since plastic bottles are also less breakable and cheaper.[4]
  2. Image titled Sterilize Water With Sunlight Step 2
    Check if the water, that you want is not turbid. If it is turbid, you have to filter it.
  3. Image titled Sterilize Water With Sunlight Step 3
    Fill the bottle with water, until it is 75% full.
    1. Put the cap on the bottle.
    2. Shake the bottle 25 times. By shaking the bottle you add more oxygen to the water. This will also improve the water's flavour.
    3. Fill the bottle until it is full.
    4. Put the cap on the bottle.
  4. Image titled Sterilize Water With Sunlight Step 4
    Put the bottle in the sunlight. A good place is a reflective surface. The sun beams contain UV-A rays that can pass through the bottle and kill most germs in the water. The oxygen helps to amplify this process.
  5. Image titled Sterilize Water With Sunlight Step 5
    Wait. The amount of time you have to wait depends on the weather.
    • If there are only little clouds in the sky, it takes 6 hours.
    • If there are about 50% or more clouds, you have to expose the bottles for 2 days to the sunlight.
    • If it is raining all time, this method doesn't work. Collect rainwater instead.


  • If a water temperature of 50°C (122°F) is reached, you only need to wait for 1 hour.[5]
  • Change your bottles, if there are too many scratches


  • This method doesn't work in a rainy environment.
  • If you're bottle is made of the wrong material, this method doesn't work. Check if the bottle is a clear PET bottle.
  • This method does not work with bottles made of glass (unless transparent glass[6]) or other materials that block UV rays.

Things You'll Need

  • A PET bottle (PET means that the bottle's material is Polyethylene terephthalate)
  • Fresh water which is not turbid

Article Info

Categories: Hazard Survival Equipment