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Are UV Water Purifiers Safe? Plus The Best UV Purifiers

UV light offers a safe and simple way to purify drinking water on the go.
UV Water Purifiers For Backpacking and Travel

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When you’re traveling or on a backcountry trip, finding clean and safe drinking water is a necessary challenge. 

You’ve probably seen someone with those little UV wands, the most common being the SteriPen by Katadyn water filter manufacturers. 

But after watching them swirling that little lightsaber around their Nalgene bottle and gulping down the contents, you’ll probably find yourself wondering; “Are UV water purifiers safe?” 

The answer is yes…and, no. 

Read on to learn the essentials for safely using an ultralight backpacking water filter like the SteriPen and find out which SteriPen to buy for travel as well as backcountry water treatment. 

Are UV Water Purifiers Safe?

UV water filters use Ultraviolet (UV) light to kill the little microorganisms that make us sick and toilet bound. 

A study published in Travel Medicine and Infectious Disease showed that when used correctly, UV water purifiers can kill 99.9% of bacteria.

For reference, this is the same if not slightly more effective than ceramic water filters.

So the short answer here, is yes, they are safe.

However, they can be unsafe. It is important to understand how UV water filters like the SteriPen work so you know when they are not safe to use. 

Incorrectly using any travel or backcountry water treatment system like UV water purifiers can expose you to harmful pathogens with the potential for serious consequences. 

When Are UV Water Purifiers Not Safe? 

As per SteriPen manufacturer guidelines, the device should not and cannot be safely used in treating water more than a light lemonade color in turbidity (murkiness). 

UV purifiers are not safe to use with murky or muddy water, or water with floating debris or material. 

To kill all the organisms in the water the light must be able to fully penetrate the contained water. 

When water is muddy or murky, UV light cannot shine through to hit all the micro-organisms. For these conditions you need a true backpacking water filter.

Muddy Water for UV Water Purification

Think of it like the sun. If its a cloudy day, chances are you won’t need to wear as much sunscreen. The sun’s effect is weakened by the murky skies. 

In the same way, SteriPens or similar UV water purifiers can only be used in clear to slightly less than clear water. 

In most backpacking or travel situations, this is manageable. 

However, for nastier conditions, you might consider ceramic filters or other filter type water purification systems.

Is SteriPen Safe For Giardia?

One of the most common microscopic parasites backpackers contend with is Giardia.

Often (unapologetically) called Beaver Fever, Giardia is found in water contaminated by human or animal feces. It causes a severe diarrheal illness that can lead to complications such as severe dehydration if not properly treated. 

According to their product specifications, SteriPen is 99.9% effective at destroying Giardia when used properly. 

UV filters are also effective at destroying another common pathogen—E. Coli. 

How The SteriPen Works

SteriPen UV Water Filter

Water purification tools like the SteriPen work by emitting UV-C light into water. This light alters the genetic structure of organisms it comes into contact with. 

By altering their structure, UV light makes these organisms unable to replicate.

Essentially, the light kills the organisms and their ability to multiply and make you sick. 

What Is UV Light?

UV light is invisible electromagnetic radiation emitted by the sun. This is the type of light generally considered to contribute to skin cancer. 

Although it is everywhere and unavoidable, UV light is actually harmful to all living organisms. 

UV water filters utilize this to help us obtain clean drinking water. 

The UV Light Spectrum

UV-B vs. UV-C

All UV light resides on a spectrum of intensity. UV-B is the light we are most exposed to in the ambient environment and the light used in tanning beds or certain medical applications. 

The light used for disinfection in UV water purifiers is UV-C; a higher wavelength spectrum of light. 

For us, the average backpacker or traveler, it doesn’t really matter which spectrum does what. 

Just know that UV-C kills things, in this case, water-born pathogens that are out to get us. 

Note: As UV-C is can be harmful to humans, you should not look directly at your UV water filter while it is operating. 

Which SteriPen To Buy: Best UV Water Filters

When used correctly, UV water filters are an ultralight and ultra effective option for both backcountry travel and international travel. 

In fact, they are so light and packable it is worth it to bring one along as a back-up on just about any adventure. 

Best SteriPen For Backpacking

When backpacking you want something rugged, reliable, and light. That’s where the SteriPen Adventurer Opti comes in.

The Adventurer Opti is the only SteriPen rated for use in cloudy water. 

Weighing in at 4 oz. it is also one of the lightest water purifiers on the market.

This purifier features a sensor indicating when water is safe to drink as well as an 8,000-liter use rating. 

The Adventurer Opti is powered by two-CR 123 batteries (included with purchase) rated to treat up to 50 liters of water before needing replacement. 

SteriPen Adventurer Opti

• Lightweight, 4oz.
• Rated for used with ‘cloudy’ water
• Clean indicator
• Purify up to 50L/set batteries

• Not rechargeable

Best UV Water Purifier For Travel

When traveling, it’s nice to save space with items that are multi-functional. 

As far as UV water purifiers go, the LARQ Bottle is one of the highest-rated UV water purifiers on the market. 

LARQ Bottle

The LARQ integrates the UV light into its bottle cap, meaning you get a high quality insulated travel bottle and a UV filter in one sleek package. 

LARQ claims that their UV lights last 40x longer than competitors and that one charge of the waterproof USB will power your bottle for up to a month. 

As an added bonus, LARQ has a self-clean function to keep your bottle bacteria free without difficult cleaning. 

LARQ Bottle

• Integrated UV light sanitizes entire bottle
• Waterproof USB rechargeable
• Insulated for warm and cold
• Lightweight and sleek
• Charitable donation with purchase

• Pricey
• UV cap only works on LARQ Bottle

Crazy Cap
Crazy Cap UV Water Bottle Filter

As the name implies, this is also a bottle cap with an integrated UV water purifier. 

The Crazy Cap is designed to be used many of the most popular reusable water bottle brands including Swell and Manna.

Crazy Cap is USB rechargeable and BPA free. 

According to the website, 5% of sales are donated to


Are UV water purifiers safe? 

Yes, they are when used correctly. UV water purifiers are capable of killing up to 99.99% or harmful bacteria in water. They should only be used in clear to slightly cloudy water or as per manufacturer specifications. 

The best UV water filter for backpacking is the SteriPen Adventurer Opti. 

For travel, our recommendation is the LARQ Bottle. 

Get the right water filter and stay healthy out there in the Crux Range. 

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