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  • Winner of both Backpacker Magazine's 2016 Editors' Choice Award and Outside Magazine's 2016 Gear of the Show Award
  • Unlike conventional hollow-fiber technology, the advanced medical-grade fibers in the Guardian block viruses—something most other hollow-fiber filters cannot do
  • Physically removes viruses, bacteria, protozoa and particulate, including hepatitis A, E. coli, giardia, cryptosporidium and more
  • Purifies 2.5 liters per min.
  • With every stroke, the purifier uses 10% of its water to flush the contaminants in its filter back into the source; this means you'll never have to hassle with back-flushing
  • Rugged construction is designed to withstand freezing and drops up to 6 ft.

Made in USA.

View all MSR Pump Water Purifiers

REI membership


Best Use Camping, Travel
Filter Type Pump
Filter Medium Advanced hollow fibers
Removes/Destroys Protozoa, Bacteria, and Viruses
Pump Force 4 pounds
Pump Strokes Per Liter 35
Output 2.5 liters per minute
Housing Material Polyurethane
BPA Free Yes
Field Cleanable Yes
Dimensions 8.2 x 4.7 x 3.5 inches
Weight 1 lb. 1.3 oz.
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In order to help compare this filter to other brands/types, what is the smallest size of particle, in microns, that this filter will remove? For instance, the First Need filter removes particles down to 4 microns.

Asked by: wildernesslovin
The filter pore size on the Guardian Purifier will be .02 microns.
Answered by: REIservice
Date published: 2017-05-09

Interested in this product, but wondering why it was pulled from REI so quickly. Was there an issue with availability? Some other reason that you can share with us?

Asked by: PatCrash
As of July 2016, we are sold out of the Guardian Purifier and are unable to backorder at this time. Please check back later as we anticipate the item being available once we receive additional orders.
Answered by: REIservice
Date published: 2017-04-04

Can you fill an Osprey water bladder or another small mouth bottle with the MSR Guardian?

Asked by: JKuck
You can use the Guardian Purifier to fill any bladder or water bottle, even if the bladder or bottle does not thread into the Guardian Purifier.
Answered by: REIservice
Date published: 2016-11-17

I have just purchased the Guardian and tried it out on some very murky water after verifying the unit through a successful integrity test.  The filtered water was quite tinted in color afterwards.  Not at all what I expected.  Is this normal?

Asked by: Windyview
The Guardian filter is working as intended and tannins (tannic acid from decomposing plant material) in the water will appear with a color when filtered.
Answered by: REIservice
Date published: 2017-04-05

Can this be used to desalinate water?

Asked by: Pamela
This purifier does not remove salt from saltwater. We, unfortunately, do not carry desalinators.
Answered by: REIservice
Date published: 2017-05-25

Should I buy a Nalgene Bottle or the this product come with one?

Asked by: Dave
​The Guardian does not come with a bottle.
Answered by: REIservice
Date published: 2017-05-30

Why was this item pulled? It's the best water filter on the market? Wish I could still buy top notch items at rei.. was waiting till my next 20% coupon to buy it, but it was gone by then.. 

Asked by: jrussell6
At the moment we are sold out of the Guardian Purifier. Please check back soon.
Answered by: REIservice
Date published: 2017-04-04

Can the MSR Guardian Purifier screw on to the threads of a MSR dromedary bag just like the purifier would to a Nalgene bottle?

Asked by: Ben H
This purifier does screw on to the threads of the MSR Dromedary Bag.
Answered by: REIservice
Date published: 2017-05-09
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