Written by: Gene Fitzgerald // Last Updated: Nov 24, 2022
This page may contain affiliate links. If you buy a product or service through such a link we earn a commission at no extra cost to you. Learn more.
Drinking germ-infested water can lead to many unpleasant health effects, so it’s only natural to look for ways to protect yourself.
UV water purifiers are marketed as one of the best methods to do so.
But does UV light really kill germs in water? Let’s find out!
Key Takeaways
UV light water purification is a water treatment method that uses UV light to kill harmful microorganisms in water. UV light purification is exceptional at eliminating waterborne bacteria, protozoa, fungi, and even viruses.
The device that carries out the water disinfection is called a UV water purifier.
UV light is perfect for destroying microorganisms. Brief exposure to UV rays of 254 nm wavelength destroys the DNA of most germs, making them unable to reproduce which renders them harmless.
Although ultraviolet light kills at least 99.99% of most microorganisms in water, there’s a small catch: UV purifiers can only perform optimally when no solid or suspended particles are in the water. This is because said particles can shield germs from the UV rays and compromise the disinfection process.
Thus, usually the best way to use a UV water purifier is to install pre-filter stages to provide for ideal water conditions.
UV light is effective against all types of germs. It works against bacteria, fungi, protozoans, and even viruses. Depending on the exact process applied, UV light kills up to 99.9999% of all germs.
Note: Although UV purifiers kill the germs in water, they don’t remove their dead bodies. So even after the germs are killed, they will continue to float in your water supply – which is not a health issue at all!
Some of the most common bacteria present in tap water include E. coli, Vibrio, and Salmonella. These bacteria are responsible for many waterborne diseases and cause gastrointestinal disturbances like vomiting, diarrhea, and intestinal cramps.
Fortunately, you can count on UV light to eliminate them.
Viruses are the tiniest form of microorganisms. They’re often present in water and typically enter our water supply through the fecal waste of humans or animals. Common viruses found in water are the Rotavirus, Adenovirus, and Hepatitis A virus.
UV light helps to deactivate these viruses. However, a higher UV dose is required.
Most protozoans in water do not pose health risks; only some are responsible for waterborne diseases. Two of these disease-causing protozoans include giardia and cryptosporidium.
UV light can eliminate these and other protozoans. But, they tend to have thick cell walls that make it harder for low-power UV light to penetrate them. So if you’re facing this type of germ, ensure that your UV light system is strong enough to kill it.
Fungi in water are especially dangerous to people who are immunocompromised. Immunocompromised people include people with chronic illnesses, the elderly, babies, and pregnant women.
Aspergillus fungi are the most common fungi found in drinking water responsible for 90% of contamination. The good news: UV light can take them out.
Using a UV system without pre-filters can give you sub-optimal results. Without pre-filtering your water, microorganisms can hide behind dirt avoiding the UV light (this issue is called shadowing).
The most basic pre-filtration for UV purification is done using a sediment filter. This filter removes dirt, rust, sand particles, and more. Depending on your water conditions, you might also need water softening, iron removal, and more.
UV water filters are not very high-maintenance, but you still need to do your part to ensure they work at full capacity. There are two parts of the UV filter we need to look at when it comes to maintenance: The UV light bulb and the quartz glass sleeve.
Testing your water after treatment helps to know if the UV disinfection process is effective.
Here are 2 ways to test your water:
Testing your water at a lab gives you detailed and accurate results. However, you have to test your water at an EPA-certified lab. The EPA has standards that all labs must meet. You can find an EPA-certified lab on the EPA website. Most states have multiple approved labs, so finding one won’t be a problem.
If you’d like to test your water yourself, then you can use a DIY water test kit. DIY kits are cheap and quite accurate. They’re also uncomplicated, so you don’t need any expert science knowledge. There are clear instructions on the pack for you to follow.
If you have any thoughts about the question, does UV light kill germs in water, please don’t hesitate to leave a comment below!
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.