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Crystal Sibson | 05.15.2018

MSR Guardian Water Purifier specs

  • Weight: 1 lb 1.3 oz
  • Dimensions: 8.2 x 4.7 x 3.5 inches
  • Flow rate: 2.5 liters per minute
  • Pore size of 0.02 microns is effective against bacteria,  particulates, protozoa and viruses
  • Cartridge Life: 10,000+ liters
  • Self-cleaning

Where to get it

$350 • MSR | Amazon | Backcountry | Moosejaw |  REI

The Bottom Line:  Whether you are backpacking through the wilderness or traveling the world, having access to clean water is a necessity. The MSR Guardian Purifier is one of the most advanced portable water purifiers on the market. Weighing in at 17.3 ounces, this filter is able to remove protozoa, bacteria, and even viruses from your water source. Being a scientist myself, I know the importance of using a good quality filter while backpacking and world traveling.

 The MSR Guardian Purifier. Photo by Crystal Sibson

Prior to purchasing the MSR Guardian purifier, I had tried several different styles of portable water filters. The first was a gravity filtration system made by Lifestraw that was easy to use but too slow when filtering water on the go. I moved on to a Lifestraw Go water bottle with a built-in filter that was easy and convenient, but it was difficult to use the bottle to filter water for cooking, so I had to pack a second filter, a Sawyer. The Sawyer Squeeze Water Filter is small and lightweight, but I wasn't a fan of trying to collect water in the provided pouches, especially in shallow sources, then having to force it through the filter by squeezing it. Not to mention it was only a 0.1 micron filter, which isn't entirely sufficient for deriving drinking water from a contaminated source. After using many different types of water filters over the years, I just wanted something better, something faster, and something reliable. I did not want to pack more than one type of filter for my needs. I wanted something I could use both in the backcountry as well as traveling to a third world country, something that removed viruses. The MSR Guardian purifier is everything that I was looking for in a filter.

Although I've only owned the MSR Guardian purifier for a short time, I am already a huge fan. It does come with a hefty price tag of $350, but the quality of the pump makes it worth the extra cash. The only drawback I've found so far is its size. It's a little bulky for backpacking and could even be considered overkill in many areas where viruses aren't a threat. As far as everything else this filter has to offer, it's fantastic! It's very easy to use and maintain. The filter is self-cleaning with every pump, so little to no maintenance is ever required. No more back flushing or scrubbing filters on a regular basis! MSR does sell a Guardian Purifier Maintenance Kit for the pump and recommends of using it once a year to help keep your purifier performing reliably for years to come.  They also recommend sterilizing the filter after extended storage, but other than that, it’s maintenance free. After use, you just pump out any excess water, towel dry the outside, and attach the clean outlet cover to the bottom of the filter. Do not disassemble and dry out the filter cartridge because a dry cartridge will not work properly. 

The best thing about the Guardian Purifier is its speed. It has the capability to purify water at a flow rate of 2.5 liters per minute, making it much faster than any other filter I have ever used. The pump itself is also threaded so you can screw it to the top of many wide mouth bottles for convenience. It fits on both my Hydroflask and Nalgene bottles, and it can even fit on some hydration bladders. The pump does not need to be attached to a bottle or bladder to function, it just makes filtering more convenient.  Very little effort is needed to fill a bottle with water, and it does so very quickly. The ease of use and speed also makes it ideal for a group outing or international trip. The filter is built to be rugged and reliable. It even offers a way to test its reliability in the field if there is ever doubt or suspected damage. Most filters do not offer a way to test their integrity in the field, and many cannot withstand freezing temperatures. MSR built and tested this filter to withstand being frozen or dropped from a height of 6 feet onto concrete. 

The ability to remove impurities down to 0.02 microns is rare in the portable filter category. Most filters have a pore size of 0.2 microns, which is 10 times larger than the Guardian's pore size; at 0.2 microns, viruses can still pass through. Viruses can’t escape the Guardian, however, so if you are using a water source where cholera, rotavirus, norovirus, or hepatitis A may be an issue, not to mention the standard cast of bacteria and protozoa, the Guardian will still deliver clean drinking water. While there are other purifiers on the market that can remove viruses, the lifespans of these products are much shorter than that of the Guardian. Overall, I highly recommend this filter if you want something fast and reliable. I love knowing that I can go on any adventure and this purifier is all I need to stay hydrated. The days of packing more than one filter are over!


I have this and it works amazing!! We got the opportunity to use it up near a stream feeding off of base Camp Muir at Mt Rainier and it was the BEST water I have ever tasted.
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