Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Become a Member

Get access to more than 30 brands, premium video, exclusive content, events, mapping, and more.

Already have an account? Sign In

Brands

Water Purifiers

Editors’ Choice 2021: MSR Guardian Gravity Purifier

Set it and forget it with this gravity-powered water purifier.

Lock Icon

Unlock this article and bundle up with Outside+.

Already have an Outside Account? Sign in

Outside+ Logo

40% Off Holiday Sale, Ends Nov. 28
$4.99 $2.99 / month*

Get the one subscription to fuel all your adventures.


  • Map your next adventure with our premium GPS apps: Gaia GPS Premium and Trailforks Pro.
  • Read unlimited digital content from 15+ brands, including Outside Magazine, Triathlete, Ski, Trail Runner, and VeloNews.
  • Watch 600+ hours of endurance challenges, cycling and skiing action, and travel documentaries.
  • Learn from the pros with expert-led online courses.
Join Outside+


*Outside memberships are billed annually. You may cancel your membership at anytime, but no refunds will be issued for payments already made. Upon cancellation, you will have access to your membership through the end of your paid year. More Details

Filtering water often starts with drawing straws. Then, the unlucky one gathers vessels, makes the trek to water to pump-and-futz, and lugs all that clean drink back to camp. Sorry, loser! With the Guardian Gravity Purifier, however, everyone wins.

Fill its 10-liter reservoir (conveniently labeled “Dirty Water”), hang it on a branch (or as high above the filter and bottle adapter as you can), loosen the hose clamp, and let gravity do its thing.

“I was impressed with its simplicity and how well it performed,” said one tester who packed the filter on a nine-person rafting trip in Utah’s Cataract Canyon. “I loved that I could fill the bag then have water at camp for the night for our whole crew. It was integral to our trip.”

The Guardian Gravity’s two-stage filter purifies water and eliminates foul tastes. A .2-micron hollow-fiber filter nixes viruses, bacteria, and protozoa, while an activated carbon stage reduces bad taste, chemicals, and heavy metals.

Essentially, this takes everything we loved about the original Guardian, a 2016 Editors’ Choice winner itself, and makes it effort-free. And, while still not cheap, it costs $100 less than its predecessor.

While it shined in a larger group setting, the Guardian Gravity is packable enough for long-haul backpacking trips. Our Editors’ Choice team enjoyed filling bottles at leisure while cooking and debating the merits of various dinner entrees. MSR claims a flow rate of one liter every two minutes. We clocked it at 2:30, but what’s half a minute when you’re sitting around digging the view while the Guardian Gravity does all the work?

When you buy something using the retail links in our stories, we may earn a small commission. We do not accept money for editorial gear reviews. Read more about our policy.