How To Purify Water With Sunlight: The Sunny Tricks

One of the time-honored methods for purifying drinking water is through sunlight. Solar disinfection has been used by people around the world since ancient times as a primary means of treating infectious waters. With a few simple steps and materials, you can turn polluted water into drinkable water using only the power of sunlight.

In this article, we will explore various ways of transforming polluted or contaminated water into potable drinking water with just the help of the sun’s energy. We will provide useful tips & tricks on how to maximize the efficiency of those methods while taking basic safety measures such as blocking harmful ultraviolet (UV) rays. If you want to learn how to give yourself and your family clean, purified and healthy drinking at home – keep reading.

Table of Contents

How to Purify Water with the Power of the Sun: A Step-by-Step Guide

Water is essential for our survival. However, the number of people who do not have access to clean water reaches over 780 million. Hence, this is considered a major global health risk. This is why it is crucial to purify water before drinking or cooking.

Purifying water can be done using different methods, but some are more effective than others. Solar purification, which uses sunlight, is among the most popular methods of removing microorganisms from water.

Step-1: Remove Obstructions to Sunlight

To make water safe, it must be able to be filtered and then disinfected. As a first step, it is important to eliminate any obstructions that may be in the way of the sunlight.

  • Remove any obstructions that may impede exposure of the water to sunlight for a long enough period. These include leaves, twigs, sticks, etc. You should try to keep these items out of the path of the light rays coming from the sun.
  • Ensure the water’s surface does not get covered up when collecting the water. Collecting the water directly into containers rather than letting it flow through pipes is best.
  • Avoid placing objects near the container holding the water. They could block the sunlight and prevent it from reaching the water.
  • Keep the container away from trees so they don’t absorb too much energy. Trees release carbon dioxide, which makes them good absorbers of CO₂. When CO₂ enters the atmosphere, it causes climate change.
  • Use plastic bottles instead of glass ones since they won’t break easily. Glass breaks easily and releases harmful substances like lead into the environment.

Step-2: Position Your Container in Contact with Direct Sunlight

Getting your water container in the right place is essential to purifying it with sunlight. It’s important to position your container so it’s in contact with direct sunlight, not just indirect light. This means you should place your container outside where no trees or buildings are blocking the sun’s rays. If possible, try to find a location on a rooftop or balcony that will receive maximum exposure to the sun.

Step-3: Wait Until the Light Has Reached Its Peak Strength

waiting until the peak strength of the sunlight has been reached. If you wait too early, the water might still contain bacteria, even though it looks clear. On the contrary, if you wait too late, the water will lose clarity due to evaporation. To determine whether the sunlight has reached its maximum intensity, look at the color of the sky. If it is bright blue, then the sunlight has reached its peak.

Step-4: Place the Container in the Sun for at Least 6 Hours

Once you have determined that the sunlight has reached its peak, it is time to place your container in direct sunlight. You should leave it there for at least 6 hours. This will ensure that all bacteria and other contaminants are killed off. During this time, ensure no trees or buildings are blocking the sun’s rays.

Step-5: Test the Water for Contamination

Once the 6 hours have passed, it is time to test the water for contamination. Take a sample of the water and place it in a sterile container. Then, take a few drops of chlorine bleach and add them to the container. If the water turns cloudy or bubbly, contaminants are still present. If it remains clear, then the water has been successfully purified with sunlight.

Step-6: Enjoy Your Purified Water

Finally, it is time to enjoy your purified water. Sun drinking is a great way to get clean, fresh water without chemicals or additives. With just a few simple steps, you can easily purify your drinking water with the sun’s power.

Benefits of Solar Water Purification

Keeping water under sunlight has many benefits. The benefits are included herewith:

  • UVA rays may activate the oxygen in water, forming hydrogen peroxide and oxygen-free radicals that kill pathogens.
  • The merit of keeping the bottle under sunlight is to speed up the disinfection progress.
  • The process is inexpensive and portable and only needs plastic bottles and sunlight.
  • The rays of UVA destroy the cell structure of pathogens.

Things to keep in Mind While Purify Water With Sunlight

If water is not sun exposed properly, it is unsafe to drink. This type of water may cause illness. For overcast weather, a longer exposure time is essential if the sunlight is not strong enough. Then you need to consider the following issues:

Bottle material

PVC materials or some glass resist ultraviolet rays from reaching the water. So commonly used a bottle that is made of PET are suggested. The handling of the bottle is more convenient in the case of PET bottles. UVB rays, Polycarbonate blocks all UVA are not suggested to use.

A bottle having no color is suggested then the colored bottles. Suppose the green of some lime soda or lemon pop bottles.

Aging of plastic bottles

SODIS efficiency relies on the physical condition of the plastic bottle, up to scratches or other signs of wear, lessening the efficiency of SODIS. Old, heavily scratched and blind bottles need to replace.

Shape of containers

The intensity of the UV radiation becomes lessened with the increase of water depth. If the water depth is 10 cm and turbidity is 26 NTU, UV-A radiation reduces to 50%. Soft PET bottles are found easily and most appreciating for SODIS application.


Sunlight makes highly reactive forms of oxygen over water. The reactive molecules help to take part in the process of microorganisms. Under the general condition, water holds sufficient oxygen and must not be created before the application of SODIS.

Leaching of bottle material

There are questions about whether plastic drinking water containers remove toxic components or chemicals from water. The Swiss Federal Laboratories for Materials Testing and Research tested diffusions of phthalates or adipates from reused and new PET bottles during solar exposure.

The result found in the water after 17 hours is 60 degrees C; water is far below the WHO drinking water standard. In the same way, the concentration of adipate and phthalate is higher in tap water.

Think about the PET bottles of water. A report published by researchers from the University of Heidelberg released antimony from the PET bottles for mineral and soft drinks stored for a few months in the supermarket.

Regrowth of bacteria

If you remove it from sunlight, the rest of the bacteria will reproduce again in the dark. This is the outcome of a study in 2010 that just ten parts per million of hydrogen peroxide is very active in preventing the regrowth of wild Salmonella.

Frequently Asked Questions [FAQs]

1. Does the Sun’s Current Strength Matter When it Comes to Water Purification?

UV photons can kill bacteria and viruses, while the sun’s rays can break down organic compounds in water. However, this still doesn’t negate the need to filter the water before you drink it. You don’t want to get sick after drinking something purified using solar power.

2. How Much Sunlight is Required to Render Unsafe Drinking Water Safe?

Solar energy is needed to purify drinking water depending on its physical and chemical properties. Pollutants like dust or smoke particles can also contaminate sunlight. Several studies suggest that sunlight is necessary to make drinking water safe. If you live in an area with sunshine for six hours a day, your water only needs to be boiled for 15 minutes. You will have to use electricity or firewood if sunlight isn’t available during those six hours.

3. What is the solar energy needed to purify water?

The boiling point of pure ethanol at sea level is 78.3 degrees Celsius. Therefore, purifying water with pure ethanol would require a significant amount of solar energy. The boiling point of pure ethanol at sea level is 78.3 degrees Celsius. The higher the temperature, the more intense the heat, and the larger the amount required to distill alcohol, which is how you can purify water with heat.

4. How Much Time Will Sunlight Purification Take for the Process to Finish?

The filtering process depends on how much water you need to filter and how long you leave it to filter. Generally, filling a single glass of water takes two to three hours, 10-20 days for a pond, and 4-6 weeks for an artificial lake.

5. When Should You Add Salt to Your Solar Disinfection Process?

Saltwater treatment involves heating the water to about 50°C to dissolve all the salt particles. This process will kill any bacteria in the water. In solar disinfection, salt helps increase the contact time between UV radiation and microorganisms. It also helps to prevent organic growth on equipment surfaces.


Water is essential for life. Unfortunately, most people don’t drink enough pure drinking water. They rely instead on tap water, bottled water, or soft drinks. These types of beverages aren’t good for our health. Fortunately, we now know how to make safe drinking water using natural methods. We’ve learned how to purify water using sunlight. Now, you don’t need to spend much on a water purifier.


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