• Home
  • /
  • Camping
  • /
  • American Overlander: MSR Guardian Water Purification System

American Overlander: MSR Guardian Water Purification System

I am not predisposed to hyperbole and I don’t spend my superlatives carelessly. So, when I say the new MSR Guardian water filter is the most advanced piece of outdoor technology I have seen in the last decade, I commit to that statement with confidence. Just the backstory of its development is impressive. Commissioned by the U.S. government to develop a water purification solution for use by military persons throughout the globe, the MSR engineering team spent more than six years designing the Guardian. The end result is a water treatment system with performance and features which far exceed that of any previous product. They have in one fell swoop redefined what a portable water purification system can achieve. And it’s now available to the consumer.


The entire unit is not small, but it is compact and easy to manage. The quality of the entire kit is superb and in keeping with the elevated level of perfection MSR is known for.


For decades water treatment options were broken into two distinct categories. There were water filters which mechanically removed harmful pathogens from the water, and there were purifiers which didn’t always remove those biological elements, but rather neutralized them, typically with chemicals like iodine impregnated elements, or even UV light. The reason for the chemical treatment was simple enough. Filters typically only removed organisms larger than .2 microns in size. Viruses, some of which can be waterborne, are far smaller than .2 microns, so mechanically removing them was extremely difficult. Filtering out tiny viruses has been made possible in recent years, but often with filters that clog too easily, thus reducing their utility. MSR, through their new Guardian, found a way to crack that problem.



The Guardian threads onto most standard water bottles and MSR’s own Dromedary bags eliminating the need for an “out” hose, which invariably gets contaminated during the pumping process.


There are a handful of criteria that define any good water treatment system. The obvious function is the effective removal of all microbilogical threats whether they are protozoa, bacteria, or viruses. A good system must also produce high volumes of water with minimal effort. Anyone who has had a filter get clogged on the first liter also understands how critical it is that a system be able to process water with a high degree of sediment. Lastly, it must be easy to use, durable, and let us not forget the cost of replacement filter elements, which can be quite expensive.

With an appreciation for the difficulty of the challenge, MSR’s engineering team managed to deliver a near perfect product.



Using their own proprietary hollow fiber technology, the Guardian can remove large particulates like dirt and silt. It can physically remove larger bio-hazards like giardia, cryptosporidium, and other harmful protozoa. Bacteria such as salmonella, e.coli, and cholera are eliminated. Most impressively, the new technology can neutralize the threat of viruses like Norwalk, Rotavirus, and Hepatitis A.


The pump employs a mechanical lever to reduce pump force. When treating water for large groups, that has a big payoff after processing several gallons in one sitting. The white mesh pre-filter is easy to clean and very effective. The unique dual hose configuration is terminated at a foam float which keeps the hoses from contacting the bottom of a water source where sediment and debris are most likely to enter the intake.



If you travel in even small groups, having a water solution that can process a large amount of water quickly is essential. For many years, a fast filter could churn out a steady flow of one liter per minute. The Guardian’s lever-assisted pump can produce an impressive 2.5 liters of water in just 60 seconds.



Self Cleaning

One of my favorite pumps of the last many years is also an MSR product, the popular HyperFlow filter. True to its name, it’s capable of moving lots of water quickly, that is until it clogs, which it invariably does here in the Southwest. To clean it, the process includes a time consuming dismantling of the pump, a back-flush, and then reassembly. In the dark or with cold hands, it is a major bummer. To clean the Guardian, the user––does nothing. It cleans itself. By recycling 10% of the clean water produced with each pump stroke back into the filter element, the Guardian remains clean throughout the entire life cycle of the filter element.




Years ago when I was working in the outdoor retail industry, people would ask me how long a filter should last. I’d reply, “I don’t know, how deep is a hole?” There are too many unknowns to assess filter longevity, many have to do with water quality and how diligently the user cleans the filter element. With the Guardian, the self-cleaning feature means the element will very likely reach its whopping 10,000-liter estimated service life. That’s a tremendous amount of water.


The unique filaments in the filtration element are visible through the body of the pump.


Ease of use

MSR pumps have always been very user friendly and thankfully, they chose to build the Guardian around the familiar format of the MSR Waterworks, which has been around for nearly two decades. With no “out” hose to contaminate, and a base that threads onto most bottle and container solutions, the Guardian is easy to use with two hands, not the three required by many systems. The pump action is light, easy, and the overall ergonomics are well designed.


Size and weight

No filter will ever be light enough, or small enough, to meet everyone’s lofty expectations. I have “pocket” filters, and they perform as well as can be expected given their displacement in my pack. There is a weight and size penalty for the Guardian’s elevated level of performance, but most people will find that offset worth their while. I might not be so inclined to use it as a soloist system for use where water quality is better than average, but for even paired travel, or extended travel in places were water quality is dubious, it’s a perfect tool.


The verdict

Because the Guardian is such a new product, I have yet to really put it through the wringer. The initial tests have been compelling, particularly with regard to the speed at which the Guardian can fill a bottle. I continue to increase the level of sediment I force through the unit, and I’m amazed that it hasn’t shown any ill effects. Time will tell, and I intend to report on the Guardian’s field performance as the year progresses. Until then, color me impressed.



MSRP: $350



Christophe Noel is a journalist from Prescott, Arizona. Born into a family of backcountry enthusiasts, Christophe grew up backpacking the mountains and deserts of the American West. An avid cyclist and bikepacker, he also has a passion for motorcycles, travel, food and overlanding.