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How to Kill Viruses in Water

Scott Winfield
Last Updated on
by Scott Winfield

Have you ever wondered how to kill viruses in water? Whether in your home or on a trip, you need to ensure your water is safe to drink.

This article discusses how viruses get in your water and how to kill them.

How to Kill Viruses in Water

How Viruses Get in Water

The most common way viruses spread is through contact with fecal material from an infected person or animal. Water can become contaminated when infected fecal material gets into the water.

Contamination is common in surface waters such as streams and lakes in the wild. Animals defecate on the ground, and rainwater runoff washes the faecal material into the lake or stream.

For this reason, you should never drink directly from an open water source like a lake.

Viruses can also contaminate drinking water wells. Contamination can occur when the well is not sealed correctly, and contaminated surface water leaks into the well.

Even in appropriately constructed wells, viruses can get into the water. Raw sewage that is not treated correctly can make its way into the water table and enter wells.

The most common cause of this is leaking septic systems. 

The most popular viruses that impact water systems are noroviruses and rotaviruses. These viruses can cause people to become ill with intestinal issues and diarrhea.

If you’ve ever had food poisoning, there is a good chance you had a norovirus.

Different Methods to Remove Viruses From Water

The best way to remove viruses from water depends on the situation. Boiling water works great, but is not the best large scale treatment option.

Some of the most common methods for how to remove viruses in water are:

  • Boiling – heating the water to a rolling boil for at least one minute
  • Chemical treatment – adding chlorine or iodine to the water
  • UV lights – exposing the water to ultraviolet radiation
  • Ozone – adding the gas ozone to water
  • Ultrafiltration – pushing the water through a microscopic filter to physically remove the viruses


Boiling water is a sure-fire way to kill viruses in water. Heat inactivates the virus in water, essentially killing it. To kill all the viruses, you will need to boil the water for at least one minute.


In high elevation areas over 6,500 feet, boil water for at least 3 minutes to kill viruses.

Once the water is boiled and viruses killed, the water can be cooled and used. For storing water after disinfection, you must use a clean container. Store the treated water in the refrigerator.

Chemical Treatment

The most common chemical used for killing viruses in water is chlorine. Most municipal water utilities use chlorine to disinfect drinking water.

Chemical Treatment
Chemical Treatment

Chlorine comes in many different forms like gas, liquid, and powder.

For individuals trying to remove viruses from water, regular household bleach will work. That’s right, the same stuff you use to get your whites whiter also kills viruses in your drinking water.

Many back-country hikers are familiar with iodine tablets. Iodine tablets are a convenient way to treat surface water when camping. But, they are not practical for large-scale use.

When using chlorine you need to be aware that chemicals have a shelf life. Old chlorine is less effective at killing viruses in water than fresh chlorine.

UV Lights

Ultraviolet lights are used in many places to kill viruses and bacteria. Ultraviolet light causes damage to the virus’s genetic structure killing them in as little as a few minutes.

UV Lights
UV Lights

One drawback of ultraviolet light is that the virus needs to be close to the light to work. Also, if there is sediment or turbidity in the water, it can block the light shading and protect the virus.

Also, ultraviolet light doesn’t have a residual effect. Once the water passes the ultraviolet light new bacteria and viruses can grow in the water.


When most people think of ozone, they think of the protective layer of the atmosphere over the earth.


Ozone is a gas that is highly reactive with organic compounds. It can be manufactured and used to treat water.

Ozone is a molecule made up of three oxygen atoms. Ozone is unstable and oxidizes things like bacteria and viruses removing them from the water.

Treating water with ozone will kill viruses. However, ozone treatment is somewhat expensive. It is not a widely used process and not something you would typically use for your home.



Most people are familiar with the water filters you add to your faucet to remove bad taste.

These filters rely on activated carbon and other materials to remove sediment and odors, but they can’t remove viruses.

Viruses are extremely small and can move through most filters. Ultrafiltration is needed to remove viruses.

Ultrafiltration involves using filters with super tiny pores that viruses can’t pass through. Typically ultrafiltration involves the use of membrane filters.

Membrane filters use permeable membranes that allow water to pass through but do not allow viruses to pass.

The Best Water Filter for Bacteria and Viruses

The Best Water Filter for Bacteria and Viruses
The Best Water Filter for Bacteria and Viruses

Viruses are very small, with the smallest measuring only 12 nanometers. That is about 1/1000th the width of human hair. Due to its small size, it’s rare to find water filters that actually remove bacteria.

Even ultrafiltration is only moderately effective in removing viruses.

Given the limited effectiveness of filters in removing viruses, using disinfection alongside filters is encouraged.

Using a filter in combination with disinfection is the most effective way to remove viruses from water.

There are whole-home filtration systems that use filters and disinfection like UV Light Systems.

These systems first filter the water through a standard carbon filter or a membrane filter, then treat the water with ultraviolet light.

For backcountry use, there are several portable filters on the market. Not all of these filters remove viruses. As with whole-home systems, it is safer to use both filtration and disinfection. 

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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