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  • MSR - Guardian Purifier System - One Color

MSR Guardian Purifier System


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    18 Reviews


    Enjoy the freshest water you've ever tasted.

    Drinking straight from crystalline mountain streams is nice in principle, but a lot less awesome when you end up running for the bushes every five minutes for the rest of the trip. There are plenty of ways to help save yourself from waterborne bummers, but none that are as effective, easy to use, and reliable as the MSR Guardian Purifier System. Developed for, and in conjunction with, the US military, the Guardian uses new Hollow Fiber technology to filter out just about everything (protozoa, bacteria, particulate, and even viruses), so you can sip fresh, clean water without first checking that you packed extra TP.

    The Guardian has an easy pump-action design that can filter up to 2.5 liters per minute, and an ingenious self-cleaning design—10% of the water from every stroke flushes contaminants from the filter, so it never gets clogged or becomes less effective. The wastewater is discharged through a tube that runs parallel to the intake, so it empties easily back into the water source. MSR also included a water-bottle adapter for easy fill-ups, and a cartridge life indicator that lets you know when it's time to switch (although the included filter is good for at least 10,000L, so it might be a while before it's that time).

    • Pump-action purifier for backpacking and trekking
    • Self-cleaning design for easy maintenance in the field
    • Effective against protozoa, bacteria, viruses, and particulate
    • Water bottle adapter ensures convenient refilling
    • Cartridge life indicator lets you know when its time to replace
    • Item #CAS008I

    Tech Specs

    Purifying Element
    Hollow Fiber
    protozoa, bacteria, viruses, particulate
    Pore Size
    0.02 micron
    Cartridge Life
    10,000+ L
    2.5L / min, 30/35 strokes / L
    Field Cleanable
    water bottle adapter, cartride replacement indicator
    8 x 5in
    Claimed Weight
    1lb 1oz
    Recommended Use
    camping, backpacking
    Manufacturer Warranty
    limited 3 years

    Tech Specs

    • Reviews
    • Q & A

    What do you think about this product?

    Have questions about this product?

    Efficiency is key

    • Familiarity: I've used it several times

    After years of using squeeze bottles and gravity bags, this filtration system has changed the game for me. Taking a fraction of the time and being so user-friendly makes this system far superior to most. The best part about the filtration system is being Nalgene compatible, such a cool feature!

    Must Have Water Supply

    • Familiarity: I've put it through the wringer

    This is expensive but absolutely necessary for long haul trips into the backcountry or otherwise remote destinations where fresh water is not readily accessible and/or you have to travel light.

    Haven't gotten sick once but have seen plenty of friends get giardia and get knocked out from the symptoms.

    There are critics who don't like the long tube or the big handle. I like both because the long tube gives you some latitude in placing the water suction in a particular place in a lake or river (ideally a cleaner area with less debris), and the larger handle makes it a lot easier to pump multiple gallons of water if you are trying to get clean water for storage or cooking.

    The longer tube is also helpful for preventing cross-contamination where the smaller self-contained units can get cross contamination since the filtered vs. non-filtered water are often right next to each other or an errant splash can contaminate the filtered water.

    This is expensive but it is worth every penny if you know how to use it and need to pump more than just a couple sips or a personal water supply.

    Love it! My best splurge in a very long

    • Familiarity: I've used it several times

    Although a bit of a splurge given the price--there are cheaper options that will generally get the job done--this works, it works fast, and it gives me peace of mind no matter the water source. I like the freedom of being able to go anywhere and everywhere without worrying about whether I will find a suitable water source (if you haven't seen MSR's promotional video for this being tested in the Cordillera Blanca then definitely check it out below; that's what sold me on it and I have not been disappointed). Now my entire group drinks with confidence no matter the water source!

    Self Cleaning System Needs Upgrade

    • Familiarity: I've put it through the wringer

    This is a phenomenal filter. Simple to use and quick but a bit on the heavy side.
    However, I broke one of them on my last long hike. It is as if the filter clogs and doesn't back-flush very well. Pump get harder and harder to use over time leading to the handle breaking off due to pressure (in my case). MSR has GREAT customer service and replaced the filter quickly. However, I could feel the new one slowing down and starting to get more difficult to pump. Would highly recommend purchasing after they improve backflushing.

    For simplicity and weight, I have switched to a GravityWorks


      I haven’t had a chance to really put this through the wringer but I know it is amazing! I spend most of my packing in high mountains and have access to “clean” water so this pump is probably overkill...but why not? I have been using the MSR miniworks and am sold on MSR.

      real light and fast.

        Super good and the water was tasty. the pump is nice and fast, while being quite as well. my only complaint is that it doesn't include a hose for the water coming out to place in a bladder or other bottle that does fit the typical screw on bottle

        Great Water Purifier

        • Familiarity: I've used it several times

        We spent a lot of time researching and reading multiple reviews on water purifiers. We even went to local stores to test and handle the different options and the Guardian Purifier System is super easy to use and won out - hands down.

        The red cap on the bottom of the purifier is simple and easy to twist on and off. This will keep the outlet hose clean and prevent it from being contaminated. The hose wraps around the purifier for easy storage and fits well in the carry case. The handle is super easy to pump.

        We recently took this on a trip and was able to fill a 2 gallon collapsible water jug in about 10 minutes. So far, I have only used the Guardian in clear water and it works great. When attaching the bladder hose to the bottom of the purifier, my 3L bladder is filled in 1-2 minutes.

        The only down side to this product is that the prefilter is supposed to sit under the water. If you don't hold the purifier just right, the prefilter will partially come out of the water or will pop out all the way due to the hose being rigid. Find the right way to hold the purifier to keep the hose straight and the prefilter in the water and this will flow quickly and efficiently. Overall, a fantastic purchase and super lightweight. Great buy!

        MSR Guardian Purifier: Self-Cleaning

        With military-grade engineering and game-changing technology, the Guardian Purifier is simply the safest, easiest way to purify water virtually anywhere on earth.

        Wont leave home without it.

        • Familiarity: I've used it several times

        I used this on a group trek to Everest Base Camp in Nepal where the rivers, streams, and glaciers, while beautiful, are teeming with human and animal waste. The guys in the group all had various methods and systems of purification, and by day 3 they were all lining up while I pumped their water from the Guardian. They were all so impressed that they were abandoning their systems and looking to buy the Guardian when they returned. The shear ease, reliability, and rate of production makes the Guardian worth the extra money. If you are planning on traveling anywhere that requires a water purification system, or even filtering for that matter, you won't be disappointed with this pump.

        Clear in look and taste for once

        • Familiarity: I've put it through the wringer

        On the pct my 3 liters were running low so I decided to test this on a really nasty small pond in Oregon. To my surprise the water went from a dark green/brownish color to completely clear. Ok it's going to taste like crap though right? Not even a little. It tasted great! Better than the smart water bottle I still had partially filled with hotel water. I ended up using it everywhere even though I really may not have needed to just because it was so fast and easy, why not? It was always worth it, even if simply to improve to the taste of my chicken teriyaki meal I was about to rehydrate:) I highly recommend this purifier! I will always be looking anywhere else to shed ounces as the Guardian will be an essential part of my backcountry kit for years to come.

        Amazing water treatment system.

        • Familiarity: I've put it through the wringer

        I was able to get this purifier through MSR on a pro deal discount and it is in my opinion the best way to treat water out there. I am a volunteer in Uganda and have to treat all of my drinking water so this being a 1 step solution makes it as easy and quick as possible. I've been using this everyday since June (a little over 8 months as of this writing) and have had no issues. I normally retrieve water from a clear water source but I have also used it retrieving water from murky lakes and streams when back packing and it always gives clear, safe, good tasting drinking water.
        It's not the smallest thing to pack, but this minor negative is by far out weighed by all the perks.
        - Never having to back flush
        - Removes virus and bacteria, which as someone who teaches water sanitation here geeked out about that they have finally made a filter type purifier, making a one step method to safe drinking water. No more boiling or UV required.
        -Is pretty quick, I can feel up my nalgene bottle in little time.
        - One filter cartridge last a very long time. For me this was a big reason to get it. Getting things shipped to me here in Uganda isn't the easiest so I wanted something that would last a while and this so far has.
        Overall. Get it, it's expensive but that's just because it's that awesome.

        UPDATE: I've now used this filter over 2 years and it's still working just as good as the day I got it. I ordered the maintenance kit after a year and it was super easy to do. After 2 years of use I would still recommend this filter to anyone

        Sweet sucker!

        • Familiarity: I've used it once or twice and have initial impressions

        I used it this weekend in the melting snow. It pumps super fast and the water is great! I love mountain water! it was way lighter Then I thought it would be too. With it being military grade i thought it would be super heavy. Not so.

        Life expectancy -- 15 liters.

        • Familiarity: I've used it once or twice and have initial impressions

        I purchased the MSR Guardian after speaking with MSR on 3 different occasions as well as several local shops. All assured me the Guardian was the perfect filter to take to the Grand Canyon to filter silty water. After filtering 15 liters of moderately silty water the filter died, all the water was being returned via the outlet hose. Following the directions, I cleaned the pressure relief valve but found it to be perfectly clean. The next step in the instructions is to replace the filter, unfortunately not an option deep in a remote section of the Grand Canyon. The filter appeared to be perfectly clean.

        When I called MSR, they admitted the Guardian has problems with silty water and was told “we’ve had problems with this pump”. Of course this is unacceptable since they advertise this pump as being made for “worse case sediment”. This ruined a 7 day backpack and forced us to hike out and drive 50 miles to purchase some treatment tables. I should have had a backup but everyone I talked to about this pump assured me of it's reliability. I expected much more of this product and from MSR Customer service.

        Robert P, thanks for your review. We are sorry to hear that you had a poor first experience with the Guardian. After reviewing your particular Guardian it appears that a great deal of ultrafine, clay-like silt entered into the purifier and sealed off the filter head. While the integrity of the filter was not compromised (would not pass through virus, bacteria, or protozoa), the reduced flow was on account of this high sediment level. High levels of ultrafine sediment will impact the filter more quickly than other types of particulate matter. When dealing with this type of water, it’s best to let particulate matter settle out of solution first, either in a small pool or a bucket, if available.

        MSR’s customer service team strives to provide as much information as possible to either help fix the problem, or get the unit in question back so our engineers can identify the issue. As the Guardian is a fairly new product, we ask that the customer provide as much accurate information about the scenario under which the problem occurred so we can work to prevent similar issues for other customers in the future or at least educate customers on proper usage. As all of our products have a limited lifetime warranty, we will either fix or replace the product in question.

        Mmmm Water

        • Familiarity: I've used it several times

        When I look at filters, I take flow, maintenance, and what gets eliminated into consideration. I'm not much of an ultralight backpacker, so weight isn't a huge deal. When it comes to my top considerations, the Guardian wins at all three.
        First, it's fast! I've been upset with several other filters that claim to pump water at 1L/min, and 5-10 minutes later my Nalgene still isn't full.
        The Guardian though, easily filled my Nalgene within 30 seconds of continuous pumping. I'd even fill my 10L Dromedary bladder with this thing! The handle is long, providing better leverage so you don't get fatigued as fast. The pre-filter also doesn't have to be completely submerged to suck water, so you don't have to worry about managing the hose to get the pump working at full flow.
        Second, the upkeep of this is so easy. Just toss the hose pre-filter in the water, pump what you need, then wrap it back up. There's no need to flush the system, wipe the filter element, etc.
        Finally, the Guardian filters all of the nasties! I'm 100% confident drinking the water that this filter pumps out, as long as I'm not directly downstream of a sewage treatment plant (More of a personal rule than a fear of the Guardian not doing its job).

        MSR Water Research Lab

        Go behind the scenes of MSR's world-class water research lab to learn about the work our on-staff water scientists do.

        The lab is located at our Seattle headquarters, in close proximity to our production lines, and is staffed by five scientists with advanced degrees in chemical engineering, biochemistry, microbiology, environmental science and cellular and molecular biology. The world inside this small space is fascinating, with an incredible amount of scientific knowledge. Here’s a look inside.

        The Guardian is fantastic

        • Familiarity: I've used it several times

        The system is extremely easy to use while in the field. You unravel the hose which wraps around the housing of the Guardian and then just drop it right into your water source. From there you can attach a Nalgene or I use the Dromlite for backpacking. It's a bit heavy at about 1 lb., however I think the peace of mind is worth it. I also don't have to deal with the slow output of Sawyer every time I take a drink, which drives me nuts. Plus this is actually a purifier and is blocking viruses where others are just filters and don't block as many nasties. With all of these new viruses coming out I think it's becoming essential to actually purify the water.

        MSR has great customer service and builds great products. It's great to have an all in one solution for purifying water.

        Unanswered Question

        Dear Sir:

        I was looking at the MSR Guardian Filter. We typically filter from a one gallon jug to another one gallon jug.
        Thus a couple of questions.
        Can you attach an outlet hose making it easier to pump from one jug to another?
        Since the filter back flushes. I would guess we should only pump 3/4 gallon of water before getting a new supply for the jug. Thoughts?

        Holy crap, it is finally here! I cannot wait for someone to review the Guardian - so cool! We need pics and videos, let's see some pump races!

        Best Answer


        I've had one of these for about two months now and am pretty stoked on it.

        I'll get a review written up and some photos.

        So to you and any one else, feel free to hit me up with questions.