The Guardian is the latest and greatest from MSR and wins our Top Pick Award for the best filter for international use. The Guardian is the fastest of all the pumps we tested, the easiest to operate and maintain, and filters out bacteria, protozoa, and viruses. We would bring this hefty model with us on international trips where we do not trust the water for extensive group filtering. This product does come with a hefty $350 price tag.
MSR Guardian Purifier Review
Compare prices at 3 resellers Pros: Filters viruses, durable, fast
Cons: Heavy, expensive
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Our Analysis and Test Results
The Guardian will guard you against particulate, bacteria, protozoa, and viruses on all your travels. It is so easy to use that pumping won't feel like much of a chore anymore.
We gave the Guardian a 10 out of 10 in this category. First, it is a purifier pump, meaning it eliminates all pathogens from the water. This includes viruses, which not many pumps like the Katadyn Vario or the MSR Miniworks EX can claim since their pore size is too large to filter the tiniest of all dangerous organisms: viruses. The Guardian has a pore size of .02 microns in its hollow fiber filter, so small even viruses can't escape like Norovirus/Norwalk, Rotavirus, and Hepatitis A.
All the other pump filters we tested have 0.2 micron sized pores, which is small enough for cysts, protozoa, and bacteria but not viruses. The Sawyer Mini has a pore size of .1 microns, but that still won't cut it for the smallest of microorganisms. However, the Sawyer S2 Foam Filter does treat viruses. The Guardian lasts for up to 10,000 liters, far more than any other pump in this review, the closest being the Katadyn Vario that can handle 2000 liters in its lifespan. We love that this pump requires zero maintenance. The Guardian has an innovative self-cleaning system that back-flushes the filter with each pump stroke. It has an additional outlet hose for the backflushed water that is right beside the intake hose, which you will never confuse with the clean water outlet.
MSR has freeze and drop tested this filter so you'll never have to worry about the integrity of your filter if it is left out in below freezing temps overnight. Every other model in this review advises the consumer not to let their filter unit freeze. Often a filter freezes, you will not be able to tell if it has any small cracks; it is challenging to know if your filter is still filtering what it's supposed to. The Guardian was also tested to withstand drops up to six feet on concrete. That is a reliable filter!
Ease of Use
This contender is the easiest pump filter to use, out of all models that we tested. There is very little pressure on the handle when pumping and it feels smooth and easy while pumping. There is also no assembly required, unlike with the MSR Sweetwater; you just take the pump out of its carrying case, take off the outlet cover and get pumping!
We usually don't like pumping our water and prefer gravity filters like the Platypus GravityWorks, our Editors' Choice winner, but the Guardian makes pumping a lot more enjoyable. The Katadyn Vario is also speedy and easy to pump and could be a good option if you do not need to filter out viruses.
Sometimes the intake hose's float gets turned around in the water source, and so the sucking is less efficient; because of this, you need to watch and make sure that it is oriented for the most efficient pump. It may also present a problem in shallow or small water sources because the float is quite large.
This award winner has a lifespan of 10,000 liters, which is huge for a pump style filter. The Aquamira Frontier Max also treats viruses but only has a lifespan of 120 gallons. The SteriPEN Ultra and the Sawyer Mini can treat up to 8000 liters and 100,000 gallons respectively, but are only good for personal use, not extensive group treatment.
Because of the Guardian's speed, we think this purifier is an excellent choice for filtering water for a large group. If you are on an international expedition, this could be a decent choice to bring along for the group.
We time-tested this model and were shocked at how quickly it filters water compared to other hand pump filters. Clocking in at a mere 42 seconds per liter, we would have no problem pumping out water for a whole group in a few minutes. The only other filter that comes close is the Vario at 47 seconds, but the Vario does not filter out viruses. Other pump filters average around 1:30. It was refreshing to have a pump that was so efficient. The fastest gravity filter, the Katadyn Gravity Camp 6L, produced one liter in 40 seconds.
The fact that the Guardian continuously self-cleans with each stroke means that the pump speed and ease of each stroke should in theory never change. When ceramic filters like the MSR MiniWorks EX see heavy use, the model gets clogged, and it becomes slower and more difficult to pump (until you take the filter unit out and clean it). We suspect this will never become an issue with the Guardian.
A purifier that accomplishes so much unsurprisingly weighs a lot, too. The Guardian Purifier weighs a hefty 22 ounces and is the heaviest system in this review.
Its weight is the main reason we would not recommend this filter for backcountry travel in Canada or the U.S. It is not necessary to filter viruses in our neck of the woods and carrying this purifier around in the high alpine spaces of the U.S. or Canada would be like watering a flower with a fire hose.
That being said, in the weight category, we would recommend this purifier for all your backcountry and front country travel internationally, especially to developing nations where sanitation in villages and in the mountains may be an issue. MSR does a good job demonstrating this application in their video that you can find at the bottom of this page.
Here's the kicker about the Guardian: it costs $350 and is the most expensive filter or purification system in this review. Nothing else comes close — the next most expensive system we tested was the MSR Trail Base at $140. We think this purifier would be a good investment for someone who owns a guide service for instance and runs international expeditions. It is super durable and has a long lifespan, which means expedition members could abuse it at a low impact. If you'll only be in the front country when traveling internationally, the Sawyer S2 Foam Filter is a good, much cheaper option. For someone who wants to go backpacking in the good old U.S. of A., we'd recommend a gravity filter like the MSR Autoflow or a personal filtration system like the Sawyer Mini or MSR TrailShot.
We were super pleased with how well the Guardian performed. It was easy to pump, and we love that it cleans itself. It takes our Top Pick Award because of its performance and the capability of this filter pump to get rid of viruses. This thing is, it's the Porsche of all water treatment systems, and not all of us can afford it, or even want a Porsche. Some of us just need a Volvo, that is reliable and hardworking, like the Aquamira Treatment Drops. If you are traveling internationally and want to protect yourself from viruses and other icky things in the water you may come across, the Guardian may be a worthy investment — especially if you can split the cost with a travel buddy.
— Jessica Haist