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How Does a UV Filter Work?

Have you ever wondered how does e UV filter work? We have the answer right here!

UV water filters use ultraviolet light to deactivate microorganisms’ cells. They are highly effective against Giardia, Cryptosporidium, Dysentery, Salmonella, Hepatitis B, and E. Coli.

The UV light destroys bacteria, viruses, and other pathogens’ ability to multiply and cause disease. It does so by damaging their nucleic acid by forming covalent bonds between adjacent bases inside their DNA. But enough scientific talk. Let’s see how a UV filter works, what its uses are, and how efficient it is in the long run.

How does a UV filter work?

The filter works by exposing the water to UV-C rays, which are efficient at destroying 99.9% of microorganisms. It’s similar to the ultraviolet rays emitted by the sun during hot summers. Just like we humans are not meant to stay exposed to these rays for long, the same goes for bacteria. It’s just that bacteria don’t know how to use sunscreen.

And since the rays are so close, their effect is instant. It takes less than a second for them to destroy the pathogens. These rays are very effective against chlorine-resistant bacteria. And the best part is they don’t require much electricity to work. And unlike chlorine, a UV filter leaves no byproducts. It leaves no pollution traces at all.

Does a UV filter work for your home?

UV water filters are one of the only four disinfection methods approved by the FDA. Yes, even the US Food & Drug Administration has given its approval to UV filtration. And we all know how hard they give their approval to new things. And since there are no chemicals to handle, you can rest assured it’s safe to use.

Ultraviolet filters are also relatively easy to maintain. They only require you to change the light bulb and quartz sleeve once a year. The quartz sleeve that surrounds the lamp is essential for transmitting the light efficiently. You need to make sure that it is cleaned properly before installing it. But the cleaning process is seamless, so it won’t cause any headaches.

It is important to note that UV filters work best in tandem with other filtration systems, such as pre-filters. The UV light will only work if the water is clear. If your water is murky or contains “floaties,” UV light won’t be useful at all. It only works on microorganisms, not heavy metals, salts, chlorine, pharmaceuticals, or other man-made substances.

UV filters are even more recommended if your water source is a private well. Or if you store your water in a storage tank. Bacteria and organic organisms like giardia, e-Coli, and others are naturally occurring in wells. And these organisms cause thousands of documented health cases each year.

Pros and cons of using a UV water filter

Of course, like with all things in life, UV water filters come with their own set of strengths and drawbacks. By glancing over these facts, it will be easier to decide if a UV filter is the right choice for you.

The pros of using a UV filter:

  • No chemicals whatsoever. Ultraviolet light works just like ordinary light. It doesn’t leave any chemical traces on the things that it touches. So it’s completely safe to handle.
  • Highly effective – UV light destroys 99.99% of microorganisms.
  • Eco-friendly – UV is probably the most environmentally friendly alternative to chlorination. It emits no byproducts and doesn’t affect your septic system. It wastes no water, and it doesn’t consume much electricity.
  • Low maintenance – you only need to change the light bulb and quartz sleeve once a year. There are no dirty filters or media to dispose of ever.
  • FDA approved – it was thoroughly tested by the Food and Drug Administration, which concluded that it’s a reliable method of disinfecting water.

The drawbacks of using a UV water filter:

  • UV light doesn’t remove other contaminants than microorganisms. Heavy metals, salts, chlorine, or man-made contaminants are immune to UV. And they will block the light from eliminating bacteria and viruses.
  • UV filters use electricity. While they don’t consume much of it, if the power goes out, the unit stops working. This might be a significant disadvantage in an emergency or a survival situation.
  • If you have hard water or if other pollutants contaminate your water, you will need a pre-filter. Or another filtration system to work in tandem with the UV water filter.

Is getting a water filter worth it?

Yes, because bacteria and viruses can appear when you least expect them. Local and state-wide authorities put in great efforts to make sure water pollution is considerably reduced. But they are still human, and they can make mistakes.

For example, the E. Coli outbreak in Walkerton, Canada, went unnoticed until many people started going to the doctor. The subsequent lab tests revealed that the local water plant had been infected with the bacteria, and people had been drinking the diseased water without realizing it.

If the residents had installed UV water filters, they wouldn’t have gotten infected. The main takeaway from this incident is that you can’t trust your local authorities to provide clean water constantly. You need to take matters into your own hands. If you combine a whole house water filter with a UV filter, you’ll be safe from both man-made pollutants as well as bacteria and viruses.

Where can I find a good UV water filter?

You can check out our Whole House UV Water Filter here. Unlike typical UV water filters, this model offers Spiralight technology. When water flows, it goes through a spiral, giving the bulb more coverage and even higher chances of neutralizing bacteria.

Instead of traditional O-rings and end caps that can crack the quartz tube if not tighten carefully, we use two sealing gaskets that are more effective. Our filter is encased in a carbon-fiber body with more powerful lamps. Instead of the traditional 15 mm tubes, we use a 19mm tube, which increases the energy that mends the water. This means you’ll get better output with the same energy consumption as other UV filters.

Best of all, it’s easy to install. Even first-timers can do it without any trouble. You need zero plumbing skills to do it. It comes with two well-built metal clips that are strong enough to keep the unit in place.  Plus that with our filter you’ll only need to change the bulb once per year.

Other manufacturers have bulbs that are rated at fewer working hours, so you’ll probably need to change them once every six or eight months if you’re lucky. With the Yarna UV Water Filter, you get maximum efficiency for minimum effort.

Now that we’ve got all of that out of the way, here are some of the most frequent questions people have asked us:


Frequently asked questions


  • Can I use this filter and a water descaler at the same time?

Yes, the two go well together. The water descaler turns calcium and magnesium crystals into ions, meaning that light has no trouble passing through or around them. So not only is the descaler compatible with the UV water filter, it is actually recommended.

  • Can’t I just use a regular water filter and be done with it?

Regular water filters can usually handle only metals, dirt, debris, or man-made pollutants. Regular bacteria and viruses can easily pass through the filter’s membrane. Cartridge filters, carbon filters, pitcher style filters do not remove E coli. The bacteria are too small and simply pass through these filters. Filters containing activated carbon are a great place for bacteria to grow and multiply. This is why you need a UV filter.

  • Is my private well really that susceptible to bacteria?

Yes, private wells are the perfect place for bacterial growth. Private wells have no governmental oversight. The Environmental Protection Agency considers them to be the owner’s sole responsibility. You should test the water in your well at least once in two years. Regular testing, of course, is recommended. And because well water is so susceptible to bacteria, a UV filter isn’t just recommended. It’s a must-have.

  • Which is better: an RO or a UV water filter?

This depends on what your specific needs are. If you have a variety of other pollutants that the reverse osmosis filter can remove, it might be worth looking into it. However, don’t forget that reverse osmosis filters need frequent membrane replacements. And they consume a lot of water. They’re incredible water wasters, actually. Plus that you’ll also get reduced water pressure as a result. A UV water filter, on the other hand, doesn’t present these problems. As long as you’ve got a reliable pre-filtration system for dissolved solids, chemicals, and sediment, it can handle any bacteria, virus, or parasite that you can imagine.

  • How do I know if my UV light is working?

On the Yarna 13 GPM and 18 GPM UV water filters, you won’t need to go through any hassle to see if the unit is doing its job properly. All you need to do is look on the side of the filter where there is a UV light indicator. It reflects the light directly from the UV bulb itself, so it’s not just an LED power indicator like on other units. That way, you’ll know exactly if the bulb is on and if it’s working. No need to go through the hassle of disassembling the unit if you don’t have to. It presents a major advantage in the unlikely event that the bulb goes bad before its one-year lifespan.

  • How long does it take for UV light to kill algae?

If you plan on using a UV water filter for an aquarium, algae is one of the main concerns that you’ll want removed. Being an organic material, the UV sterilizer works wonders for it as well. In addition to destroying bacteria, ultra-violet sterilizers can help reduce the spread of free-floating algae, however, whilst it will kill algal blooms, it will not actually eradicate them. A UV sterilizer is not a replacement for good biological and mechanical filter, which is still necessary to physically remove algae from the water. However, once you remove the large clumps of algae, you’ll have no more problem with it building up again once you start using the UV sterilizer.

  • What happens if you touch a UV light?

Exposure to UV light can burn skin and is dangerous for the eyes. Don’t touch the bulb with your bare hands. After you unplug the filter, leave it rest for at least 15 minutes so that it has time to cool down. Follow the instructions in the user manual carefully and replace the bulb as necessary, typically after one year of use.


The bottom line: does a UV filter work?

The UV water filter works best with clear water. It won’t catch rust or dirt, but it will stop dangerous bacteria. It ensures that you won’t catch any disease from drinking water that was filtered with UV. Make sure also to install a pre-filter if your water has dirt or metals in it. If you have hard water, you can pair the UV filter with a water descaler.

There’s a good reason why UV water filters are one of the four FDA-approved methods of disinfecting water. They have been thoroughly tested and have proved that they work. And unlike chlorine or other disinfectants, they don’t use chemicals or leave pollutants behind. And they don’t waste any water whatsoever.

If you live on a farm, having a UV water filter is essential. Your livestock is susceptible to disease, and they can transmit it further. So you are in far more danger. Especially if your private well is near animals. Or if you use pesticides, fertilizers, and other pollutants near it. Or even if your well gets cracked, corroded, or damaged. You have no idea how easy it is for bacteria to form in such a place.

And you’re not entirely safe in cities either. Remember, local authorities can also mess up from time to time. Earlier in the article, we gave a relatively recent example from Walkerton, Canada. Something similar can happen in any US town or city any day.