MSR Guardian Purifier Water Filter Review
JUMP TO: SPECS | PROS & CONS | HOW IT PERFORMED | FEATURES | SUMMARY
Author: Steve Edgerton | Updated: Oct 10, 2023
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Compared to most backpacking water filters, the MSR Guardian Purifier is equivalent to bringing a tank to a knife fight. While other filtration systems usually guarantee safely purified water in most conditions, the Guardian comes as close as possible to always guaranteeing it — in all conditions.
Although the Guardian is impressively effective at purifying water of any quality, it is also heavy, bulky, and expensive. The filter system is overkill for your standard weekend backpacking trip. But if your explorations often tend toward the edges of the map — trekking in developing countries, trails with dodgy water sources (think sludgy bogs and silty creeks), or extended remote expeditions where waterborne pathogens could be life-threatening — then the tank-like durability, ease of use, and reassuring reliability of the MSR Guardian has no equal.
SPECS
MEASURED WEIGHT: 20.4 oz / 578.3 g
FILTER MATERIAL: Hollow Fiber
FILTER LIFESPAN: 10,000+ liters
FILTER PORE SIZE: 0.02 microns
FLOW RATE: 2 liters/min
EFFECTIVE AGAINST: Bacteria, protozoa, viruses, sediment, and microplastics
PROS
Effectively filters out sediment, microplastics, bacteria, protozoa, and viruses
Impressive flow rate for a hand pump filter
Self-cleaning and easy to use
Extremely durable: filter can even withstand freezing conditions
CONS
Very expensive
Too heavy and bulky to be your “daily driver” backpacking water filter
Does not filter chemicals or heavy metals
HOW IT PERFORMED
SETUP & FLOW RATE: With multiple hoses, filters, caps, and other various adornments, the Guardian looks complex and intimidating. But setting it up and using it in the field is delightfully simple. All the essentials come installed and ready for use. Toss the hose in your source water and begin pumping into your container. The filter even screws right onto a wide-mouth bottle, like standard 1 or 2-liter Nalgenes, for spill-free filtration.
The ergonomic hand pump facilitates efficient filtration and fast flow rates. In relatively clear water, the Guardian fills a 1-liter bottle in just over 30 seconds.
The Guardian is easy to use right out of the box. The long hose, impressive flow rates, and ability to secure it right onto a wide-mouth water bottle facilitate a quick and efficient filtration process.
WATER QUALITY: The Guardian features two filters: one blocking larger sediment from even entering the hose, and then the primary hollow fiber filter. The hollow fiber filter is high-quality and durable, with a 0.02-micron pore size. Even pulling from turgid, sediment-heavy water sources, water always comes through the filter looking impossibly clear and clean — free from all bacteria, protozoa, and even viruses, which are too small for most backcountry filters to catch. The Guardian was designed to exceed US military testing standards for “worst-case” water conditions. I have not and hope to never experience those conditions in the backcountry, but the Guardian appears to be more than up to the task.
Despite the filter’s impressive performance, it does not feature activated carbon to remove industrial chemicals and heavy metals. Fortunately, this never proves an issue for the vast majority of backcountry uses.
WEIGHT: It is hard to be a tank without weighing like a tank. The Guardian is far and away one of the heaviest backpacking filters out there, with an all-in weight of more than 20 oz. But that is the price you pay for bulletproof performance.
PACKABILITY: The packability of the filter correlates to its weight. The Guardian is a filter really only worth bringing when you have to. It is simply overkill for any trail with reasonably safe and reliable water sources.
Though by no means the most packable filter, the Guardian does neatly store away into its included zippered bag.
DURABILITY: The Guardian has outstanding build quality. Unlike almost all other backpacking filters, it still functions after being subjected to freezing temperatures, a huge advantage for alpine expeditions. It is also self-cleaning. A second hose continually backflushes the filter as you pump. The pump requires minimal maintenance and maintains a strong flow rate even when filtering very turbid water. The hollow fiber filter cartridge has an advertised life span of 10,000+ liters of water.
NOTABLE FEATURES
FREEZE-RESISTANT: I do most of my backcountry camping close to home in the Canadian Rockies, where clean, clear water sources are abundant and viruses are not an issue. However, below-freezing temperatures are also abundant, so the freeze-resistance of the Guardian’s hollow fiber filter is a huge selling point. Although its filtration capabilities go far beyond what I need, its reliability in cold temperatures is sometimes reason enough to bring it along for trips deep in the shoulder season.
HOSE FILTER: The mesh attachment on the end of the intake hose acts as a pre-filter, preventing larger sediment from even reaching the pump filter in the first place. The dual-filter system ultimately extends the pump’s lifespan and keeps maintenance to a minimum.
A pre-filter on the hose screens out large sediment from even entering the Guardian’s primary filter.
0.02 MICRON PORE SIZE: The pores of the Guardian’s hollow fiber filter are an order of magnitude smaller than most other backpacking filters. At 0.02 microns, the filter effectively captures viruses and very small particulate matter, like microplastics.
HAND PUMP: The Guardian’s large, ergonomic pump is comfortable and efficient. Pumping large quantities is still a bit of a workout, but this design is as good as any pump filter I’ve ever used.
The efficient, hassle-free hand pump adds to the Guardian’s efficiency.
WATER BOTTLE COMPATIBILITY: The ability to screw the filter securely onto a water bottle is a nice touch that makes filtering even easier as it frees both hands for pumping. It is worth noting that having a wide opening on your container is more or less essential. Unless you have two sets of hands, it is almost impossible to direct the flow of filtered water into something like a Smartwater bottle or soft flask.
A wide-mouth water bottle can be screwed on in place of the storage cap to make the filtration process significantly easier.
SUMMARY
With its efficient flow rates, durable construction, and ability to filter even the nastiest water with ease, the performance of the MSR Guardian Purifier is second to none. But it is also heavier, bulkier, and far pricier than most backcountry filter alternatives.
Ultimately, it is best to think of this filter as a specialty tool: its extreme capabilities are best suited for trips with extreme demands. If you’re looking for a filter primarily for weekend trips or trails with solid water supplies, dropping the cash on a filter like this simply is not warranted. But if your adventures include international treks, guiding large groups, or remote expeditions where reliability is paramount, then the MSR Guardian is a worthy investment that will likely last a lifetime, paying for itself many times over.
DISCLOSURE
MSR provided me with a free sample for this review – but the views expressed here are all my own. The review might also contain affiliate links, which help us keep churning out more content.
MORE INFORMATION
If you want to compare the MSR Guardian against other options then check out our review of the Best Backpacking Water Filters & Purifiers, or for a review of something more compact and lightweight see our comparison of the Sawyer Squeeze Water Filters.
If you are getting kitted out for the trail then be sure to check out our Ultimate Backpacking Gear List.
Or for more information on hiking and backpacking, check out some of our other tips and gear reviews:
Or check out our entire Gear Reviews Page, our Knowledge Base Articles, or Destination Guides for more hiking, backpacking, and outdoors related content.
Happy hiking and take care out there in the wild!