Does Steripen Work?

Does Steripen Work Featured Image 2

I purchased a SteriPen UV filter a few years back. It was, in all honesty, a bit of a snap-purchase after the element on my MSR hand pump filter cracked and I didn’t trust it any longer. I always carried iodine tablets as a back-up, but UV filtration was all-the-rage so I thought I’d give it a try. There are still, admittedly, times when it feels like you’re trying to purify your water with a magic wand, so today we’re going to explore the question: does Steripen work?

How Does UV Purification Work?

does steripen work - steripen ultra UV

The science behind the effectiveness of ultraviolet (UV) purification is sound. The most notable source of UV radiation on Earth is the sun. In my last article, I spoke about the effects of UV radiation from the sun on standing bodies of water, and how that might actually make them a cleaner source to pull from than moving streams, creeks, or rivers.

UV water filters work the same as the sun, but on a smaller scale. At particular intensities, UV light emits substantial radiation to kill the DNA in bacteria and other microorganisms. In effect, UV rays penetrate harmful pathogens in your water and destroy illness-causing protozoa, eliminating their ability to reproduce.

Most UV water filters, including all models of Steripen, contain a light source capable of an output around 254 nanometers which, in the condensed space where they’re used, is of significantly greater intensity than the radiation produced by sunlight.

Is UV Radiation A Standalone Solution?

When used as directed, Steripen boasts the ability to destroy 99.9999% of bacteria, 99.99% of viruses, and 99.9% of protozoa. The benefits of UV filtration include the fact that it is chemical-free, requires very little energy, is taste and odor-free, doesn’t need much maintenance, and is extremely effective.

While the percentages above speak for themselves (check out this study for more info!), many companies still recommend, however, that you use multiple methods of water filtration to ensure the absolute cleanliness of your drinking water. This is especially the case if the water you’re trying to purify isn’t clear.

This is a big point: the effectiveness of the Steripen isn’t guaranteed, and only reaches this near-100-percent success rate in water that is extremely clear. Darker water won’t allow UV radiation to penetrate throughout and, as a result, should always be additionally filtered using other methods to guarantee safety.

How To Use The Steripen

Using the Steripen is a fairly simple process, but can be a bit troublesome if you’re not familiar with it. As I mentioned at the start of this post, it feels a bit like waving a magic wand around in your water for a while in hopes of eradicating bacteria, and as I explain the actual process, perhaps you’ll understand why.

For starters, many models come with a 40-micron pre-filter that attaches to the top of a one-liter Nalgene bottle. This catches larger bacteria and protozoa as you scoop water from the source.

The most important thing to note here is that the sensors must be dry for them to work effectively. This means, as I found out the hard way, you’ll need to dry them off between each use if you’re unsuccessful in your first attempt.

Once you have your bottle full and the protective cap removed from your pen, you’ll need to push the button. One push will purify a half-liter and two pushes will set your pen to purify a full liter. The green LED on the pen will begin flashing (for no more than 15 seconds). This indicates the pen is ready to use.

While the green LED is still flashing, dip the pen into the water until the lamp and sensors are completely immersed. The pen will automatically detect the water and the UV light will come on. Now you’ll need to continually agitate the water by stirring the pen until the UV light turns off. At this point, the green LED should turn solid and the dose will be complete.

*Important note: if the red LED turns on after you’ve agitated the water for some time, this means the dose is incomplete, and it is best to dry off the light and sensors and give it another shot. Always make sure to thoroughly dry the pen’s light and sensors before storing.

UV Filtration vs. The Competition

All told, there are about eight different methods of water purification. All offer varying levels of effectiveness, and many concerned hikers (especially in high-traffic areas known for greater quantities of protozoa and bacteria) will use multiple methods in conjunction with one another.

This graphic is a nice study of the effectiveness of different water purification methods from a sample of 2013-14 distance hikers:

does steripen work - filtration type comp table

Comparing Steripen Models

There are five models of Steripen to choose from. For my part, I have the Steripen 3 Classic, which requires four AA batteries which are not included with purchase. Some newer models can be recharged via USB.

Here’s a full table for comparison:

does steripen work - model comparison 1

Final Verdict On The Steripen!

I’ve used some form of water filtration for my entire backpacking career. First, it was MSR and now it’s Steripen. My overwhelming conclusion is that (knock on wood) I’ve never gotten sick!

While it took a while to get used to (and have full faith in) I now find my Steripen incredibly useful and it’s much lighter to carry than the previous water filter I lugged around for years. Overall, I give the Steripen my stamp of approval when it comes to the most important resource on the trail!

Share Your Steripen Experience!

hiking the ruby mountains - roads end trailhead
The Backpack Guide (Tuck) at left and Jabronie Joe on right @ Road’s End Trailhead

At The Backpack Guide, I’m always looking for new trails and wildernesses to explore and I’m also interested in the experiences of others in the wild. I want to know which type of filtration method you prefer, why, and if you’ve ever had a harrowing experience related to water filtration in the backcountry.

If you decide to purchase a Steripen after reading this review, I’d love to know how you like it after you’ve had the chance to use it a few times!

Feel free to reach out to me directly (email below), or share your latest adventure or backpack by tagging @thebackpackguide on Instagram and Facebook!

I hope you’ve enjoyed this review of the Steripen and I’d love to hear your feedback in the comments section below. I’ll be quick to reply to any questions, comments, or concerns you feel like sharing!

Here’s to Filters, My Friends!

The Backpack Guide










  • Lightweight and Easy to Carry
  • Push-Button Operation
  • Quick Purification Solution


  • You're Not Always Sure if The "Purification Cycle" Was Complete
  • Runs on Batteries (which sucks if you forget batteries!!)


  1. Remy

    Hello Tucker,
    I have been working in and around municipal water treatment plants for decades now and actually stumbled across your site when researching a problem one of my client is having.
    The large scale water treatment plants (the ones that supply drinking water to thousands of people) us UV sterilisation technology but as a last line of defence after all the physical filtration technologies have done their job then the chemical cleaning technologies have done their job.
    If I was stuck in out the wilderness trying to fashion up something to get drinking water I would definitely be looking at combining the technologies in a similar fashion.

    1. Post
      Tucker Ballister

      Hey Remy! 

      Thanks for the comment! I think you hit the nail on the head as far as being “better safe than sorry” goes. Improper water filtration can ruin even the best laid plans in the backcountry, so using multiple methods of filtration is always going to be a safe bet! 

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