Can Water Filters Remove Viruses? The Surprising Answer

Water filtration systems are really good at removing lots of different contaminants. From heavy metals like lead and mercury to pesticides and chlorine, filtration systems treat most contaminants. 

But what about viruses?

Viruses are the smallest class of organisms making them a lot harder to remove. At  about 1000 times smaller than a single grain of salt, viruses are smaller than even the smallest bacteria. As a result, lots of viruses go undetected into water systems where they are consumed by unsuspecting people. 

Although not all viruses pose a threat to their host cells, others can wreak quite a bit of havoc on the human body. 

For some help sorting through your options, checkout Dispozal's roundup of the best water purifiers.


What Is A Virus

In order to understand why a virus is so small it may help to take a look at its components and how it works. A single virus cell (also called a virion) only has two components: A set of instructions (RNA or DNA) on the interior, and a protein covering on the exterior. 

This class of “organism” is so primitive that it cannot exist alone and must essentially hijack a host cell in order to survive. 

Once inside the host, all the virus can do is replicate itself and either kills the host cell or gives instructions to the cell to kill itself. 


Because no known cure exists for viruses, the treatment for an infected person often falls to the immune system in the person’s body to fight off the unwanted organism.. 

This is why you may have been told by a doctor that a viral illness needs to “run its course”. 

Individual vaccines are developed for specific viruses and can protect a person from becoming infected in the first place. However these vaccines are no guarantee that a person won’t become infected, in part because viruses are good at mutating which can render a vaccine obsolete in treating the original virus. 

Even though our bodies are skilled at fighting these invisible villains, viruses sometimes manage to hold our cells hostage. 

Since dealing with a virus after infection isn’t easy, the best scenario is to keep away from viruses before they make it into our cells. For those concerned with treating viruses in drinking water, the answer to the problem may surprise you. Despite the challenge of removing something so small from water, there is a tried-and-true method of treating viruses in drinking water and it has been used for over 100 years. 

The key is that we don’t actually remove the viruses. Instead we damage them so that they can’t complete their mission of harming a host cell.  

We do this with UV rays.

Ultraviolet Light

Sunlight is a natural disinfectant thanks to its ultraviolet radiation, and these UV wavelengths come in three varieties; UV-A, UV-B and UV-C.  All three offer some protection against viruses,but the most potent of the three is UV-C light which kills up to 99.99% of viruses. 

UV Rays

UV Rays, in particular UV-C, can kill up to 99.99% of viruses in your drinking water.

UV radiation works by ruining the instructions inside the virus making it completely useless. Once the nucleic acid (RNA or DNA) is damaged the virus can’t accomplish its goal of reproducing and killing off the host cell and therefore poses no threat whatsoever to the host.

Thus, a water purifier equipped with a UV filter is your best line of defense for your source of drinking water.

UV Filter Features And Considerations

There are three main features and factors to consider when researching the right UV water purifier. We’ll cover them in detail here.

Testing your own water

When purchasing a UV water purifier the first step is to know your water and what you are treating. We recommend getting water tested for different levels of bacteria and viruses before deciding on a particular UV system. Many systems treat the whole house but others can be part of a filtration system like reverse osmosis (RO) or a carbon filtration system. Be sure to check with the manufacturer for the levels that the system requires before treatment. In some cases pretreating water can be necessary.


When purchasing a whole house UV system it is important to know the volume needs of your home. UV purifiers measure output in gallons per minute (GPM) and the biggest factor in determining the size of your system is the number of bathrooms in your home. Again, check with the manufacturer about which system is recommended for your home so you don’t end up having an insufficient water supply. 

UV Dose

Lastly, make sure to know the correct amount of UV energy needed to treat the organisms in your water. Getting the correct strength or dose of UV radiation will be the difference between killing those viruses and bacteria effectively or not. 

Certain organisms require a very specific UV dosing which is measured in something called millijoules per square centimeter of water. Having that original report on what is lurking in your water can help take the guesswork out of what strength you may need in order to treat your water. 


Remember that although you may be filtering your water and effectively removing many harmful substances, in order to bacteria and viruses, you need ultraviolet light radiation. 

To recap: This is due to the size of these microorganisms (too small for filtering out) and how the UV radiation changes the internal structure of the virus. 

After testing your water to know what needs to be treated, deciding on the kind of UV system based on volume and UV strength as well as point of entry or source is the next step. You can refer to our roundup of best water purifiers for viruses and bacteria for some help in that department.

This technology helps make certain that viruses, despite acting so different from other contaminants, won’t stand in the way of ensuring your water is safe and healthy to drink.

2 thoughts on “Can Water Filters Remove Viruses? The Surprising Answer

  • Sharing is caring. Thanks for sharing this with the community. We must filter water before drinking it. I agree. It also true that earlier we found a different taste of water after filtration. That’s for the materials contained in the water. Now most of the water purifiers provide the same taste water through RO water purifier as well. Drink safe, live safe.

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