MSR Guardian Purifier Review

  • Day Hiker
  • Urban Hiker

MSR Guardian Purifier Overview

When I think of the word “guardian” it conjures up images of an old-world protector, decked out in the heaviest armor, carrying a two-handed broadsword in one hand and a shield with the crest of the sun in the other. Yeah, I’m a nerd, but that description transfers pretty well to the MSR Guardian Purifier. It follows in the old tradition of hand pumping, weighs a solid amount, and is not miniscule — but it gets the job done in such a thorough, satisfying, and basic way that all those marks against it fall away. This device is, all things considered, the most badass water filter and purifier on the market.

The MSR Guardian Purifier is a water purifier that pumps roughly 2.5 liters per minute, backflushes automatically, attaches to wide-threaded bottles and bladders, and is one contained unit. It strains out protozoa, bacteria, and viruses, which is everything you’ll encounter on the trail or in cities abroad. Rightfully, the MSR Guardian Purifier is our Premium Pick for the Urban Hiker and Day Hiker.

Read the full review of the MSR Guardian Purifier below. If you’re confused about the difference between a filter and a purifier, want to know what protozoa are, or have a slight obsession with gear, check out our Guide to Water Filters and Purifiers — it’s a beast.

Guardian Purifier Specifications

Feature Type Feature Specs What This Means
Weight 21.7 oz. (615 g) The Guardian is heavy, weighing well over a pound. The case is another 2.4 ounces. High quality construction, a double tube, and a beefy filter/purifier unit make up the weight.
Filter or Purifier? Filter and Purifier The Guardian is the only filter purifier combination on the market. It takes care of anything you’ll encounter. Specifics on the difference between filters and purifiers in our Guide.
Treatment Type Pump Yes, it’s a pump filter. The pump itself is easy to grip and moves quickly when pulled. But it does take effort! Specifics on treatment types in our Guide.
Effective Against Protozoa, bacteria, and viruses All pathogens you commonly encounter in the U.S. and abroad are strained out by the MSR Guardian. Specifics on pathogens in our Guide.
Filter Pore Size (Microns) .02 microns Most known viruses in water are not smaller than .02 microns in size. Your eye can’t see this, but the Guardian can separate the water from any particles this size or bigger. Specifics on micron size in our Guide.
Filter Media Advanced Hollow Fiber Hollow fiber filters are common, but this one is special. Medical-grade, it blocks viruses, withstands near-freezing temps, and can survive falls. Also made in the U.S.
Flow Rate 2.5 liters per minute Incredibly high flow rate, especially for a pump filter. If you pump really hard you can fill your bottle or bladder quicker.
Filter Life 10,000+ liters Very long filter life. Most people won’t need to replace for years (even decades) unless you use a filter for most water consumption. You can purchase a replacement cartridge, but it’s quite expensive.
Filters Particulate? Yes Comes with a fine mesh pre-filter attached to the intake tube, meaning large particles never make it in. Then the Guardian filters smaller particulate and backflushes out anything left.
Components

Filter, tubes, and pre-filter are all one unit

Carrying case

The Guardian works out of the box with no adjustments. Everything is attached, and stays attached. Fits in a carrying case.
Works With

Standard Wide-Mouth Threads

MSR Dromedary Bags

Hydration Tube

The bottom of the Guardian screws into any standard wide-mouthed bottles or bags, like wide-mouth Nalgenes or MSR Dromedary bags. You can also attach a hydration tube.
Manufacturer Warranty 3 Year Limited Manufacturer Warranty MSR is a reputable company that stands by its products. If components of the Guardian fail, send it in.
Cost $349.95 A very high price for the only purifier filter combo on the market.

Gear Review of the MSR Guardian Purifier

Origins: Easing You In

Anything that claims to guard and purify needs to live up to the hype, and the hype for the MSR Guardian Purifier is quite large. It has been heralded with awards since its debut in 2015, and remains the most expensive and coveted water treatment system on the market. I wanted to test these claims out, in addition to stacking it up against other, much more common (and cheaper) water treatment methods like squeeze filtration, gravity filters, UV filters, and chemical treatments.

MSR-Guardian-purifier-featured
The MSR Guardian Purifier with case, tubes, and prefilter. Sexy? Yes.

To do this, and to really test the magic of the Guardian, one has to travel internationally. The “purification” aspect of this product means it filters out viruses, which is excellent for sketchy tap water and questionable streams in underdeveloped countries, but a bit overkill for your common U.S.-based backcountry lake. The Guardian still works great for both, but using it in truly dangerous water is the ultimate litmus test.

So, I went to Thailand. There are two scenarios I used the Guardian for while traveling — the first is filtering tap water before long, hot treks; the second is in the jungle next to rivers and waterfalls. The purifier performed like a powerhouse in both situations, and has continued to impress every time I take it out.

Revelation: The Moment I Knew

The revelatory moment came to me 15 minutes before a trek into the Mu Ko Lanta National Park on the southern tip of Koh Lanta, a large, chilled-out island on the Andaman Sea. My travel partner and I were prepping for the hike; it was hot season (as opposed to monsoon season), so the amount of water on the trail was unknown, and likely low. This meant we had to prep our water beforehand.

As budget travelers who don’t like waste, we were sick of buying bottled water. The Guardian Purifier was practically begging to be used, so we did. This epic moment is not a glamorous nature scene, but rather a humid, sink-filling ritual in which the Guardian Purifier became my favorite water purifier to date.

MSR-Guardian-Purifier-pumping-2
A bit of muscle required.

My accommodations had a sink with a plug, which allowed me to turn on the tap water and fill up a small reservoir of water to be filtered. I waited until the water line was about four fingers thick (a quad shot for those wondering) and uncoiled the tubes, which come attached and ready to use out of the box.

At this point I noted the prefilter and float. The prefilter is the rectangular screen at the very end of the two hoses, and it’s the part that sucks in the water. I stuck that in as best I could, though it can be hard to keep it submerged due to the float. The float is the large black foam panel attached to the tubes, which keeps the prefilter bobbing on top of the water. This can be annoying until you get the right angle, and then it keeps the prefilter down perfectly.

MSR-Guardian-purifier-sink
Sinks don’t make for pretty pictures. The prefilter is in the water, but it’s not quite full enough for the float.

I unscrewed the clean side cover (the red bottom cap), and noted the small hole underneath. This is where the filtered water comes out. I brought a wide-mouthed bottle on the trip, which threaded perfectly onto the bottom of the Guardian. If you don’t have a bottle like this (or MSR’s Dromedary bladders) you just have to line up the small hole on the Guardian with your water bottle or bladder.

MSR-Guardian-Purifier-attached-to-bottle
Wide-mouthed bottles attach to the bottom of the Guardian with ease.

Everything was in place, so I began to pump. Yes, it’s a pump filter, and for a moment I remembered all the painful backpacking trips in which I’ve filled liter after liter of water for a group, arms burning after a tiring hike. But before that thought was even finished my one liter water bottle was halfway full. Another few seconds and it was completely full.

The Guardian is really fast. So noticeably fast that my partner exclaimed, “Wow, that was easy!” She got our hydration bladder and opened it for a full three liters of pumping. The bladder was full in just over 60 seconds, and we had 4 liters of sparkling water, sans cost or waste, to take into the jungle.

Digging Deeper

There are many standout elements of the MSR Guardian Purifier, which makes sense due to its high cost. The best part, though, is the fact that all of these fancy components are in a single unit that’s ready to use the moment you take it out of the box. You can’t say that for most filters or purifiers out there, and it makes the Guardian foolproof.

The feature that a filter and purifier connoisseur will appreciate most is the automatic backflushing. The Guardian has two thick tubes: one for intake, one for backflushing. After you pull in water through the prefilter, it travels into the pumping chamber. The water is pressed down through the device into the bottom, and most of it goes into your bottle, but some of it is automatically turned away and pushed out of the second tube.

MSR-Guardian-purifier-double-hose
The tube end that is open (the upper one) is where the backflushed water comes out.

The prefilter helps to screen out sediment, but this secondary backflush mechanism makes it so that every time you filter water you are also backflushing the device. I found no slow-down of the filter rate in my month of heavy usage, and I don’t expect to in the future either.

MSR Guardian purifier prefilter
Some fine mesh on that prefilter.

The other important features are not things you can see. The Guardian filters to .02 microns, which means it gets rid of viruses. This is the only filter on the market that purifies water (the rest are chemical treatments or UV light), so if you enjoy filtering but need purification, this is the model to get. The lifespan of the cartridge is 10,000 liters, meaning you won’t need to replace it for years (unless you use it every day for all your water). It can withstand falls and cold, but in sub-freezing temperatures you want to keep it as warm as possible.

Finally, the unit comes with a nice carrying case, which has open mesh to help the exterior dry off.

MSR-Guardian-purifier-in-case

Ease of Use

Almost as simple as drinking the water you’re about to filter. Uncoil the tubes, plop the prefilter in the water, attach a bottle or hover over your bladder, and pump. No backflushing required, and no real maintenance.

A tip: to get the prefilter to settle correctly, make sure the curve of the tubes makes a circle (or close to it). That way when you pump the prefilter won’t jump out of the water, and it will stay facing the correct way.

Durability

I baby gear, so I did not drop it from a serious height or take an axe to the hoses. The plastic is very thick, the joints are well built, and it doesn’t seem like it could damage easily. You pay for that in weight, because it is heavy.

Portability

Portability is all relative, right? It’s very portable in that it comes with a case, is all one unit, and curls up into itself nicely. However, as far as other filters go, the Guardian is quite large. It weighs 22 ounces (that’s 1 pound, 6 ounces) and is roughly 8 inches long. It will fit in a day pack or larger backpack, but you’ll notice the room it’s taking up.

MSR-Guardian-purifier-size-comparison
That’s a 32-ounce Nalgene, which is a roughly the same size of the MSR Guardian. Yes, that’s a large water filter.

Filtration Rate

As I’ve already said, the filtration rate is incredible. MSR markets it as 2.5 liters per minute, and I’d agree with that. You can get it even faster if you’re pumping hard. I was blown away by this filter rate, and it seriously makes me consider taking the Guardian on all of my excursions, whether viruses are present or not.

Grievances

Could MSR have done more for its flagship, pricey, over-the-top water purifier? Yes, I think so. At $350, this is the most expensive water purifier a normal backpacker could buy, and it might be the most expensive piece of gear you own. For that price, I wish it had a few very nitpicky things.

First, there’s the hole at the bottom where the purified water comes out. It’s a small hole with a lip meant for a bladder hose to slide onto, which is nice, but not very practical. Most bladder hoses today have Quick Connects, and the Guardian should really have (and come with) an easily attachable Quick Connect port to that hole. That way I could pump water directly into my bladder without leakage or a second person to hold it. You can buy a separate adaptor kit at the moment, which also helps it filter into smaller threaded bottles, but for the price I think all that should be included.

MSR-Guardian-purifier-protecting-lid
This hole is where the water comes out. It should really have a Quick Connect in there.

Second, I wish the hoses were a little longer; they are roughly four feet. I understand why they’re not: MSR wanted them to coil perfectly around the unit, and the added length would increase weight. The length works if you filter into the screwable water bottle, but when I had to place the hole over a bottle or bladder that didn’t move seamlessly with the device itself, I found myself having to make sure everything was close at hand, even when using a sink.

MSR Guardian purifier attached to bottle 3
The hose is a decent length, but even more would make it easier to use.

Finally, I wish the float was movable or detachable. MSR engineered the prefilter to work with the float, but with river currents it often displaces the angle and gets frustrating to use because you can’t suck in water if the prefilter is sticking up. If the float was movable, you could easily adjust it to make the prefilter sink an inch below the surface while the hoses float, allowing a steady intake of water.

MSR Guardian purifier prefilter in water
As trippy and cool as this is, the prefilter is facing above the water. For best results you want it completely submerged in the water, which could happen more easily if the float was adjustable.

Final Word

The MSR Guardian Purifier is a beast. It will treat your water in seconds, cleans itself while you pump, and is one self contained unit. If you need to to thwart viruses and have the money to spend, you can’t do better.

Where to Buy MSR Guardian Purifier

The MSR Guardian Purifier was used in this test. There is only the one model, and you’ll know it when you see it. The unit is self-contained and will work alone, which is great because it’s expensive! That said, MSR offers a number of attachments, replacement parts, and a cleaning kit for the Guardian. The Universal Bottle Adapter + Clean Cover is useful if you want the Guardian to screw onto a different kind of bottle. The Dromedary bladders are excellent if you want to pump directly into a bladder. Below you’ll find the MSR Guardian Purifier.

Daniel Zweier

Daniel Zweier is Editor-in-Chief of Backpackers.com. Beyond orchestrating the daily flow of Backpackers.com, Daniel writes surrealistic short fiction and novels, adventures into the backcountry and abroad, surfs, reads, drinks tea, and obsesses over gear. A lot of gear. Visit his website if you want to learn more about his authorial pursuits.

Review Policy: We do not accept payments or gifts from brands and vendors, and strive to provide unbiased, independent advice. Brands typically provide review samples which we return, and in some cases we purchase the item so we can keep using it long after the review. Affiliate Policy: We support the hours that go into our reviews and testing through affiliate commissions on purchases made through links in this article. These don't effect the outcome of our reviews or selection of gear, as per our Review Policy.