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SteriPEN Freedom UV Purifier: A Bridge over Troubled Water

When I first got wind of the SteriPEN, I knew I had to get my hands on one and share the results with those fearless Vagabond readers who venture to go where no aristocrat has gone before: to the lands of impure water. Brita is not a household name in the third world, and a [...]


When I first got wind of the SteriPEN, I knew I had to get my hands on one and share the results with those fearless Vagabond readers who venture to go where no aristocrat has gone before: to the lands of impure water. Brita is not a household name in the third world, and a traveler should carry their own means to purify drinking water with them.

While it’s a traveler’s principal necessity, potable water is inaccessible to 1 out of 10 people globally. This means there’s a 10% chance you will get sick from a waterborne disease – a percentage which can only increase depending on where you are traveling. Devices like the SteriPEN help bring that percentage much closer to zero and can ensure that you return from Mexico with Mayan chocolate, not Montezuma’s Revenge.

Travel-Friendly Design

The specific SteriPEN I tested, the SteriPEN Freedom, was specifically designed to accommodate travelers as they pass through airport security or backpack through the Himalayas. Just 5 inches long and weighing a paltry 2.6 ounces, it slips indiscreetly into any carry-on or outer pocket, and comes with a sleek travel bag to boot. It effortlessly passed my durability test (I always throw travel products against my bed frame several times – the best simulated travel scenario I can get) and has a plastic cover measuring an entire millimeter thick. Note that the Freedom is not meant to service an entire village, but to test single-servings of water, up to 0.5 liters at a time.

Once charged (which takes about 2-3 hours depending on the charging source), using the SteriPEN seems intuitive: remove the cover, dunk it in water, and stir until the blinking green light turns solid. If all goes as planned, you have a sterile glass of H2O in a little over a minute. I even noticed a moderate improvement in the taste of the water, though it could have just been a placebo effect. Where it gets tricky is when it comes to the LED simulator guide, which it would probably pay to carry around with the device until you have it memorized. Green means the battery is charged and red means it needs charging, but there is another indicator to show when treatment failed due to low battery, and yet another indicator for when treatment has been successful but the battery is still low. There are yet two other indicators that serve as lamp warnings, and they’re about as easy to read as Morse code.


The SteriPEN also has a convenient little flashlight that flicks on/off when the device is gently rolled back and forth. It seems convenient, that is, until you don’t want the flashlight on, but it comes on anyway when you’re resorting to Italian hand movements during a demonstration (I speak from experience).

While a charger is included, the SteriPEN can be charged via USB (including the one for your phone, sparing you the weight of an extra charger) and does not need to be fully-charged in order to work. It does beg the question, however, of just how useful an electronic device would be in a nation with poor sanitation, considering that electricity is often just as scarce as drinkable water. In the absence of electricity, a solar charger can be used to charge the device…so you might as well pick up one of those, too.

Effectiveness of UV Water Purification

The biggest concern travelers might have when considering a SteriPEN purchase is whether or not they can actually trust the device to work. At an MSRP of $119.95, the Freedom does not run cheap, so is it a worthy investment? Admittedly, this reviewer was not willing to put her health on the line to test the Freedom in anything other than tap water (though in my area, it is not suggested that the tap water be consumed). Some pathogens, especially those which cause viruses, are less sensitive to UV light than others, which means that larger doses are required in order to neuter them (yes, “neuter” them – that’s the proper scientific term, since UV light prevents microbe reproduction), but this research has not been conclusive. The dosage of UV light projected through any SteriPEN device is not specified on either the product packaging or on SteriPEN’s website, so there is no way to “customize” the strength of the UV lamp. A list of what SteriPEN devices “treat” can be found here, but since viruses and bacteria are mutable, UV water purification can never deliver a 100% safety guarantee.

Misconceptions about UV Water Purification

UV water purification will NOT turn wine into water, or sludge into Aquafina. If you are stranded somewhere near the Nile and think it might be an ingenious idea to scoop some of it into your water bottle, the SteriPEN will not magically dissolve the dirt, oil, or other unknown particles floating around in the water, nor will the particles themselves necessarily be safe to ingest after UV exposure. The reason for this is simple: UV purification requires that light rays strike potentially dangerous microbes, and anything blocking those rays prevents the light from radiating throughout the content. In other words, solids act as a sort of sunscreen in your water, blocking UV rays and allowing microbes to linger unfazed and possibly reproducing. For that reason, it is suggested that you not only pre-filter particularly filthy water prior to using the SteriPEN, but also that you move the SteriPEN around in the water for the duration of the purification process in order to render the paths to hazardous microbes unobstructed.


Moreover, it’s critical to keep in mind that since UV light does not completely destroy microbes, they have the potential to reproduce after water treatment during a process called photoreactivation. Therefore, water will need to be re-treated if it is exposed to visible light for certain periods of time before consumption. This is a slippery slope, because there is no specified timespan for when visible light will begin restoring DNA molecules in harmful bacteria or viruses, and it is dependent on temperature, the type of microbe present, and the amount of UV light emitted (wavelength). However, I read in the user guide that the SteriPEN lamp emits both visible light and UV light at the same time, which means that if the SteriPEN is indeed effective, all photoreactivation research is moot. Either way, it generally seems best to drink purified water immediately after UV treatment.


If your budget affords you a UV water purifier and you envision yourself spending long periods of time in a rather unsanitary corner of the earth, you can err on the side of a SteriPEN. The Freedom, for example, allows for 8,000 water treatments, which is more than 2,100 days in the Amazon under the “8 glasses per day” rule. Not too shabby. While the device is not guaranteed to shield you from every waterborne illness, it is undoubtedly better to have than have not. As for a regular household staple, a pitcher or faucet-style filter is far more effortless (not to mention cheaper). Nevertheless, the travel-optimization of the SteriPEN freedom in terms of size, efficacy, and peace-of-mind is tough to beat.

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Filed under: Travel Gear, Travel Tech

About the Author:

Tiffany Zappulla is VagabondJourney.com’s Korea correspondent and travel tech reviewer. She pinched pennies throughout college, sacrificing parties, treats, and occasionally even food so she could start traveling to foreign lands. So far she’s toured Scotland, Spain, and Japan (twice) on a budget, and spent three years living in South Korea actively engaged in the culture and lifestyle. Aside from her qualifications in ESL, Tiffany does other freelance writing and odd jobs. She is currently living the broke American life for awhile before deciding on her next adventure. Connect with her on Google+. has written 31 posts on Vagabond Journey. Contact the author.

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  • HoboSylvain February 17, 2013, 4:55 am

    Yes, SteriPen are the choice of many travelers.  I’m about to hit the road and I’ve shopped for one.  The fact that Freedom model is USB chargeable is a big plus for travelers too… since you don’t require another wall adapter in foreign countries.
    I was about to buy the Freedom, but I discovered a few days ago a new model… the Ultra.  It has the same specs as the Freedom, including USB charge.  It is a bit bigger… but it has a nice rubber neck so you can fit it in a bottle opening.  There’s also an OLED screen which prevents the confusion you referred to in therms of light color, etc.  Finally, the Ultra model is a bit cheaper than the Freedom one.
    I spoke about those devices with a friend who works at a water treatment plant here in Canada.  He told me that UV is the ultimate treatment because it really kills anything alive.    Yes, you will ingest dead bacterias but they won’t be harmful to you in that condition… and might even help your immune system (a bit like a vaccine).

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    • Vagabond Journey February 17, 2013, 9:25 pm

      @HoboSylvain Thanks for this update about the Ultra. 
      Tiffany totally nailed my concerns about the Steripen here. Namely the fact that you need to charge it up with electricity, and if you’re away from this luxury then the thing is just a chuck of plastic. It just worries me that it is in these out of the way places that you need to depend on your water purification system the most. I suppose it’s a good thing that the times where a standard traveler are going to be beyond the realm of electricity are rare.

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      • HoboSylvain February 17, 2013, 9:28 pm

        @Vagabond Journey Well, since it’s USB powered… you can always charge it with a solar panel or use a portable power bank.
        If you want, they also have a winding model that doesn’t require electricity at all.

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  • AnnieLutes February 17, 2013, 6:59 pm

    This is a great article.  The only time I’ve ever done water purification is in the backcountry, where UV actually isn’t that great (as I’ve been told) because you treat gallons at a time, so we use the tablets.
    Nothing like drinking your first glass of water you purified yourself with floaties in it 🙂

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    • Vagabond Journey February 17, 2013, 9:21 pm

      @AnnieLutes For sure, it’s always a little frightening at first when you filter some Amazon River water and realize that it’s an odd shade of yellow 🙂

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  • Gerry April 16, 2013, 1:53 pm

    Hi Tiffany.

    Great post.
    It seems to me that tablets, plus a purifying “straw” would be a better option?
    By removing the particles, etc too?

    (Google it) – there are a few versions out there,
    Don’t want to mention any in particular in case people think I’m just advertising or something.

    There are pictures online of people using these to suck water directly from open sewers,
    Straight from water to mouth!

    Sure how wise this is, since if anything gets through, it won’t be killed.

    Anyone have any experience of those?

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