MSR Guardian Gravity Water Purifier | Review - Outdoors Magic

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MSR Guardian Gravity Water Purifier | Review

A zero-effort and high-spec purifier that’ll keep you safe on wilderness trips at home or abroad

Why We Chose It: Impressive technology, easy to use, well-built

A few years ago, MSR picked up a bunch of awards for a product called the Guardian Purifier, a mini hand pumped device that was capable of not only removing bacteria from water supply but viruses too. For 2021, they’ve taken that technology and transferred it to a new purifier that does all of the work for you. 

The Guardian Gravity purifier from MSR cleverly removes bad stuff from water without the need for any pumping, squeezing or sucking. The clue’s in the name here. All you need to do is fill up the 10-litre reservoir, hang it up at least six feet above your bottle (or whatever you’re drinking from) and let gravity do its work.

Photo: Chris Johnson

Who Is The MSR Guardian Gravity Purifier For?

With the sad fact that wilderness areas are getting increasingly polluted by human waste we all need to be more careful about drinking from natural sources when out and about. Normal portable water filters, unfortunately, might not always cut the mustard when, say, a stream, has been polluted and contains human viruses. A purifier, on the other hand, will do the job for you. So, long story short, while this kind of product will be very, very handy for international trips where waterborne viruses are common, these days, you’d even be wise to carry it on domestic backpack trips too. 

How It Works

The secret is in the purifier’s Advanced Hollow Fibre technology. This involves a bundle of spaghetti-like straws, each dotted with microscopic holes which are big enough for water molecules to pass through but too small for nasty things like bacteria, protozoa, dirt and even viruses.

Water will flow and filter through these at the rate of 1 litre every 2 minutes. Granted, that’s slower than what’s offered by most pump-actioned filters, however this has the benefit of being lighter, more packable, and capable of storing and carrying water. It’s built rugged too, using a tough PU film bladder with RF welded seams and smooth, rounded edges.

“We all need to be more careful about drinking from natural sources when out and about.”

There’s a very simple but effective way of controlling the flow, using just a little clip on the hose that you pinch in to limit the rate or halt it altogether. A cap seals the end of the hose, and this has a clever little adapter that lets you fasten a number of different types of bottles securely onto it. Cleaning it out is easy as well, all you need to do is open up the ‘purge hose’ which will flush out debris and keep the flow rate nice and high. 

When not in use, the whole thing packs up into a little ripstop pouch no bigger than Nalgene water bottle. When it comes to the end of its life, which MSR say will be after a minimum of 3000 litres, the cartridge can be replaced. Handily, there’s even an indicator on the cartridge so you’ll know when the time has come.

Photo: Chris Johnson
Photo: Chris Johnson
Photo: Chris Johnson

Tester’s Verdict

Will Renwick, editor of Outdoors Magic

“The Guardian Gravity is clearly based on MSR’s previous AutoFlow XL Gravity filter, which we liked enough to include in our Outdoor 100 2019. That model is a touch lighter, it has a faster flow rate and it’s also a heck of a lot cheaper. But, and this is big but, it can’t handle viruses, whereas the Guardian Gravity can, and it also needs backflushing to clear out whereas the Guardian is much simpler in that regard.”

“Anyway, the choice of whether you want to spend the extra money and get that virus protection is up to you. The Guardian Gravity is certainly a good product that we’ve all been impressed by here at Outdoors Magic. It’s packable, convenient, can serve large groups of people and is robust in its design without being heavy.”

Photo: Chris Johnson

MSR Guardian Gravity


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