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MSR HyperFlow Microfilter

rated 3.5 of 5 stars
photo: MSR HyperFlow Microfilter pump/gravity water filter

The MSR HyperFlow Microfilter is a lightweight, cucumber-sized water filter that utilizes hollow fiber technology to provide remarkably fast water filtration. Resembling a compact bike pump in form and function, the HyperFlow delivers up to 2 liters a minute and mates nicely with hydration bladders, Nalgene bottles, and even soda bottles.

The downside? It is susceptible to damage if dropped or exposed to freezing temperatures.

First Look: MSR HyperFlow Microfilter


MSR HyperFlow Microfilter
Weight: 7.4 oz. (209 g)
Size: 7 x 3.5 in. (19 x 7 cm)
MSRP: $99.95
Available: Spring 2008


The HyperFlow’s claim to fame is its ability to filter water quickly: 3 liters per minute, according to MSR. In our tests, typical flow was about 2 liters per minute, although we never felt at a loss for capacity. Extremely aggressive pumping may provide additional flow, though we never felt the need.

More notable than raw speed is the HyperFlow’s capacity. It takes just 20 pumps of this little filter to fill a 1-liter Nalgene. But at only 20 strokes per liter, you’ll spend as much time switching between bottles as you will actually filtering. This little pump moves a lot of water and does it with significantly less resistance than many other filters.


MSR touts the HyperFlow as the lightest filter available, although the published weight of 7.4 oz. (209 g) is within a gram of the Katadyn Mini. Our test unit was slightly heavier at 8.2 oz. (232 g) for just the pump assembly, intake tube, and prefilter. The water bottle adaptor and carrying sack (with sewn-in instructions) add another 2.8 oz. (79 g) for a total packed weight of 11 oz. (311 g).


The HyperFlow’s 0.2-micron filter is effective against bacteria, protozoa, and particulate matter. Like all non-chemical filters it does not protect against viruses. The HyperFlow does not have a charcoal filter to treat chemical contamination, so water drawn from particularly dirty sources may retain some odor and/or flavor.


The prototype filter that we tested had some durability problems. Most notably the outflow coupling (which connects the filter to the water bottle adapter or hydration hose) broke under moderate strain during use. When filtering into a water bottle, the natural pumping motion can put a lot of stress on that area.

This was not a catastrophic failure – the filter itself still produced clean water – but pumping water into the open mouth of a Nalgene became somewhat awkward, it would no longer work for pumping into a bladder, and pumping into a smaller bottle was messy at best.

MSR says this problem will be addressed in production models. In the meantime, caution is advised: this is a lightweight product, and should be treated with appropriate care.

UPDATE (8/4/2008): Since publication of this review, we've had the opportunity to test a production version of the Hyperflow. Even under exaggerated stress -- beyond what one would expect during normal operation -- the production version did not experience the problems we had with the prototype (See below for the full update.)

Field Maintenance

Unlike some pleated and ceramic filter designs, the HyperFlow’s hollow fiber filter element cannot be cleaned by scrubbing. However, the filter is designed with a backflow mode, which allows you to pump clear water backward through the filter element, flushing sediments back out the intake hose. If the filter element becomes clogged with sediment, the filter can be disassembled and two check valves turned around to reverse the flow.

The process is documented on a card sewn into the HyperFlow’s carrying sack, but it can take a little practice to get comfortable with the procedure. There are a number of pieces to keep track of and the small check valve assembly can be difficult to grip to unscrew. It’s a good idea to practice this at home a few times before needing to do it in the field.


MSR designed the HyperFlow to attach easily to most common water bottles and hydration bladders. Hydration systems and small-mouthed water bottles or soda bottles can attach directly to the filter, and MSR provides an adaptor for 63 mm bottles (Nalgene or similar). The adaptor can replace the cap on one of your wide-mouth bottles and the “cap within a cap” provides a smaller opening that pours smoothly and prevents spillage. The small cap fits snugly, but can be a bit difficult to open and close. You can also pump into wide-mouth bottles effectively without the adaptor, but you’ll want to have a stable surface on which to place your water bottle.

Ease of Use

Operation of the HyperFlow is straightforward, and it requires very little effort to pump. Connecting the filter to a wide mouth water bottle using the adaptor takes a bit of figuring out the first couple times you do it, but once learned the system is straightforward. The adaptor cap itself can be difficult to open.

Because of its small size, the HyperFlow can be a bit awkward to grip – there just isn’t room for all your fingers. We consistently found ourselves with a couple fingers gripping the outflow coupling. Handling the output end of a water filter with dirty hands can contaminate the filter and introduce germs right back into your previously clean drinking water, so paying close attention to hygiene and how you’re holding the filter is essential.

The prefilter tends to float on the surface and can get more air than water if not placed carefully, especially in moving water. This can be a good thing, or a bad thing, depending on whether your water source is afflicted with loose sediment or floating surface scum. Luckily the Velcro straps that allow you to securely wrap the host and prefilter around the filter body can also be used to secure the prefilter to a branch or rock for more precise placement when needed.


The hollow fiber technology used in the HyperFlow allows for fast, easy filtering at a very light weight. The downside is that it’s relatively fragile. Exposure to freezing temperatures will break the filter element. When water becomes trapped inside the fibers (there’s no way to completely dry them) and it freezes, its expansion causes the fibers to break, rendering them permeable to the bacteria and cysts they’re supposed to be blocking.

MSR provides a test procedure that tells you whether or not a filter is still good. This procedure can be carried out in the field, without tools, by backflushing clean water through the filter and then checking the pump’s ability to hold suction and for the presence of air bubbles in the outflow. (Of course a still-frozen filter won't pump at all, providing an excellent clue that it’s broken.)

To test this procedure, we intentionally froze a filter element and then performed the filter test per MSR's instructions. The results were mixed. While the filter didn’t act quite like a new one, it also didn’t exhibit the behavior that the directions said would indicate a broken filter. This ambiguous “maybe-broken” result didn’t provide much confidence one way or the other. More indicative to me was that listening closely I could hear the sound of air being sucked through the filter element. When in doubt, it’s best to use a new filter element or a backup treatment method. It’s also a good idea to perform the test a few times with a known-good filter element so that you know what to expect and can treat any different result with suspicion.

If there’s any chance temperatures on a trip could fall below freezing, bring an extra filter element and/or backup treatment. Also be prepared to put the filter element in a snack-size Ziploc bag and keep it near your body – inside your sleeping bag or in an inside jacket pocket.

Bottom Line

The MSR HyperFlow is one of the lightest pump filters on the market, and by far the fastest. It is comparable in size, weight, and effectiveness to the Katadyn Mini, but significantly faster, at 2 liters-per-minute (tested) compared to the Mini’s .5 liter-per-minute ceramic filter.

Because of its cold-weather limitations and potential fragility, the HyperFlow is not for everyone. But warm-weather backpackers and lightweight hikers who can’t use chemical treatment, or simply prefer a filter, will find the HyperFlow to be a welcome option for three-season trips.

MSR HyperFlow revisited August 4, 2008 at 9:09 am

hyperflow-microfilter-300x300.jpgEarlier this year I reviewed a prototype of the MSR HyperFlow Microfilter. While the prototype generally performed very well, the outflow coupling (which attaches the filter to a water bottle) broke during normal use. At the time MSR said that problem would be fixed before the filter went into production.

Well, we've been testing a production HyperFlow, and the outflow coupling seems to be much stronger and better-assembled than the same part of the prototype. Even when I put it under exaggerated stress -- beyond what one would expect during normal operation -- the HyperFlow remained solid and performed well.

That said, it's worth reiterating that the HyperFlow should be handled carefully. The manual warns that the hollow-fiber filter element can be rendered ineffective if it's dropped on a hard surface -- even if you can't see any outward signs of damage.

Luckily the HyperFlow comes with instructions on how to test for filter damage. It's a rather lengthy process, so it's a good idea to practice the required disassembly and backflushing procedure before taking the filter into the backcountry. By practicing the filter test at least once you'll have a baseline "good" test with which you can compare if you think you may have a damaged filter. The difference can be pretty subtle.

On the upside, the warning about dropping seems to be overly-cautious: after intentional rough handling and dropping, our test filter passed MSR's filter self-test with no signs of damage.

Source: received for testing via the Trailspace Review Corps (Sample provided by MSR for testing and review)

More efficient than the TrailShot and lighter than the MiniWorks, this filter is ideal for solo trips where water is free flowing and clear. Filters protozoa and bacteria, but not viruses.


  • Compact
  • Efficient
  • Easier to use than the TrailShot


  • Cost
  • Drying the filter when not being used
  • Does not filer viruses

Weighing 221g, MSR claim the Hyperflow filter works down to 0.2microns and will filter 99.99% (see the caveat there) of bacteria and protozoa with an output of 2.75l per minute though you'd have to be pumping pretty hard and fast to achieve anything like this kind of flow rate. The cartridge has a 1,000l lifespan so it will not run out anytime soon. 

I have used this on several long distance trails and I have been very pleased with its performance. It works best if water that is free flowing can be found or it is clear. I tried purifying water from a cattle trough that was green from algae and the purified water remained green. Needless to say I poured it away.

The filter comes with instructions, a long length of silicone hose and a first stage filter which blocks debris from entering the pump. Also supplied is a "quick-connect adaptor" which fits the filter to a bottle. I purchased a second quick-connect adaptor so I could keep two 750 bottles topped up. The MSR HyperFlow is easy to maintain on the trail. Simply back flush it to keep the filter clean. I bought the maintenance kit for peace of mind, but so far I have only used the oil for the 'o' ring. I did not suffer any mechanical failure in all the time that I used it.

My only quibble with the filter is how to dry the filter cartridge following a trip so it does not become clogged with bacteria or any other nasties that like a moist dark environment. I tried really hard by pumping it (though it does not seem to like being pumped with air) and standing it on end to let gravity do the work, but it still has a small amount of moisture left inside when shaken vigorously. It says not to freeze it so this is not an option either. 

Apart from the issue with drying and storing the filter, this has been a excellent buy. I have enjoyed its ease of use and my routine for topping up two 750ml bottles with the additional cap has proven to be a winning combination. If you are purifying badly contaminated water or it is being used by a group you will need to consider the MiniWorks or the Katadyn Mini ceramic filter. If it's a solo trip or with a companion, this would be an excellent choice. 


Several long distance trails in the UK including the Brecon Beacons Way, the South Downs Way, and the Jurassic Coast.

Source: bought it new
Price Paid: £80


This is the third filter my buddy and I have used. The first one was nasty, screwed to the bottle, killer to pump, low flow and cheesy filters (we'd have to pack two spare, and we pump from clear streams and lakes). 

So he gets this ceramic filter pump and it's nice, we use it one season and I think it's kind of a hassle: the pump takes two hands to use, the line to the bottle causes you to find a place a bottle can balance by itself, and the in-take line has this funky float that always moves the pick-up against the bank, or in a fast moving stream, up to the surface so you're pumping air.

I mention all those things because this one doesn't do them, none I can see.  Pop that cap on your Nalgene bottle, put on the pump, cast the pick-up line, and pump, one hand on the bottle and one pumping away. 

The flow is like, "Hey, is there a filter in this thing?" I've had the pick-up float up to the surface but got very little air, mostly it seems to pull into the heavier current.  If you don't watch out the bottle will fall off the pump, that's why I hold the cap and bottle kind of together. 

This really, just a two handed set up allows for access to stream sides that wouldn't have enough flat spaces for uncoiling two lengths of hose. Also, when you're putting it away, there's none of that, "This is the clean hose, this is the dirty hose, this one goes here and don't let it touch this other one."

When I first saw this thing I thought it looked cheesy. It does, I keep thinking I'm going to break it, but I haven't' yet. And taking it apart to back flush had me following the directions like those Christmas cartoons about Dad putting together Junior's swing set. You know, "Place tab A through the cone of left-notched filter receiver unit carefully not damaging the seat of delicately-made valve G."  Yeah, that part was a pain, but with practice I'd get better at it, kind of like telling my right from my left; I've almost got that one down. 

Price Paid: $100

I have been using this filter since it was first released. It has been performing perfectly since first pump, and at the first sign of "bogged down" filtering I back-flush as recommended and it resumes excellence. It also states to back-flush every 8 liters, which i also practice considering it only take about 3 mins to accomplish and is very simple.

The speed in which it delivers Poland Spring like filtered water is simply amazing. However, i have read several negative reviews pertaining to the filter becoming completely clogged and unusable. I looked into this dilemma and found that MSR has a phone number you can call to replace these faulty filters, apparently quite a number of them were put to market with sub par filtering performance. If you call them and give them the serial number off the filter, if it qualifies they will replace it with a more advanced filter for no charge.

I called and informed them that mine was purchased right about the time they came out and that i had no issues with the filter, they still sent me a new filter Just in case now that's customer service!

I highly recommend this product.


Price Paid: $99

Under ideal conditions - i.e. practicing with it using my tap water - it did work great. Very fast, easy to pump, lightweight, the back flushing set up with the little valves was a little daunting but not unmanageable.

Then I took it with me in the back country. I pumped less than two liters before it plugged up. I had to work so hard to get enough water to back flow it then it made me so sad to use all that hard earned clean water to send it right back out and even then it was still slow. AND, I don't know who gets the prefilter thing to float on top of the water - I have to weigh it down with a rock - but not too deep or it just sucks up dirt off the bottom. or it gets air.

I like the set up, I like the direct connect to nalgene bottles, I like using it while standing at my kitchen sink but in the field it has been worse than worthless because I know I can't trust it. I wish I had my ceramic filter back!

Price Paid: $80

I owned this product for a summer, and don't think I can recommend it.

As others have mentioned, in the beginning, and under ideal conditions, this thing works great. It's lightweight, it pumps fast, and the floating water-sucker-thing generally stays in place.

The problem, as everyone else has mentioned: It clogs up real fast, and can be difficult to clean.

I took it out with a large group doing a three-week trip. There were about 8 people and about 4 filters, including this one. It slowed down drastically -- to the point where even a single pump was a chore -- within probably 3 or 4 days.  

Backflushing, to the extent I was able to do it, was generally unsuccessful at substantially improving its performance. I won't rule out the possibility that I'm too stupid to figure out how to backflush successfully, but I did follow the directions and we had a number of people puzzling over it.  

After about 10 days out, I happened across a ranger who took a look at it and was similarly unable to figure out a way to clean it more effectively. A few days later I gave up entirely on using it.

We were using clear, flowing water, generally from streams very close to snowpack, so I wouldn't think that bad water conditions had much to do with it.

I should point out that all the filters we had ended up failing in some way before the trip was over. Sometimes pump handles snapped off, sometimes they just became impossible to clean effectively. We spent most of the last week of the trip drinking unfiltered water when close to the snowpack and using tablets when further away.

Perhaps someone with more patience and better backflushing competence would find this a lovely product, but the hassle isn't worth it from my perspective.  I've since purchased an ultraviolet purifier and find that it matches my needs much more closely than any filter I've owned.

I'm always a little skeptical of the overly enthusiastic 5 star reviewer but here goes - this thing is the real deal. I started out with purification tablets for lightweightness and after the aftertaste neutralizer my water still tasted horrible. Then I purchased the MSR Miniworks which I only used once because the yield was terribly slow and the unit was very bulky.

Enter the MSR Hyperflow; this thing is awesome!!! Much smaller than other MSR filters, easy to use, and yields about 1 liter every 30 seconds. I love it, I love it, I love it. Also, it's pretty tough, after use you can just wrap the hose around the filter and stuff it in your sack. The bottle/bladder adapter works great with my MSR Dromedary bag. The genius of this product is its ease of use and speed at which water is filtered.

Price Paid: $95

The MSR HyperFlow is really great for filtering water on the go.


  • Adaptable and replaceable parts
  • Cover for the clean side
  • Easy to operate
  • Lightweight
  • Included lid screws right on a standard sized bottle or bladder


  • Small parts that can get lost

The MSR HyperFlow is great for lightweight travel. It's quick, efficient, and easy to operate. It's very easy for one person to operate alone even with the pump action without contamination because MSR includes a bottle cap to screw right on your water holder and a clean side cover to always keep the clean side clean.  
It assembles and cleans quickly and without tools allowing you to fully flush and dry the unit inside for long life.  
The sediment filter is very effective, lightweight, and seems to prevent any debris at all from being pulled into the unit. It sits well on the surface and has a nice velcro loop (meant for storage) that you can use to set it out in the water further with a stick.  

Source: bought it new
Price Paid: $90

I'm not sure if I should be writing this review yet or not. I just got my filter in the mail this week and have not even used it in the field yet. I just wanted to point something out that I would have liked to have known before I bought mine.

While reading the operating and maintenance book I found that it recommends back flushing the filter every 8 liters or once a day. This requires disassembly and reversing the two check valves, back flushing, then taking back apart to change the valve directions to there correct position. I took mine apart and put it back together in a reasonably short time but I still don't like the idea of having to do it daily.

Gary C.

4/2105 Update:

I didn't realize that I hadn't updated this review. I had nothing but problems with hard to pump filtering and finally quit using it altogether. I bought a Steripen and never looked back.

Price Paid: $99

Nice filter. I've only used it a couple of times, but I love the flow it produces, nice weight, packs well, and keeps me hydrated.

Update: February 1, 2010

Here's my review of the MSR HyperFlow:


Even though others seem to love this filter, I have to rate it low. I had it on one trip and I couldn't even filter 2 liters of water before it plugged up to the point it was unusable. The backflushing technique did not work, even after I got back and tried flushing it with tap water.

I filtered lake water from a collapsible bucket, so silt should not have been a major problem. If I had been out for more than this short 2 day trip I would have been in trouble. Based on this performance I would not recommend this filter.

Price Paid: $100

My friends call it the MSR "Faucet". Seriously, I can't pee into a bottle as fast as this thing can fill one! Filtering daily water for a party of 4 takes only a few minutes.

I back-flush mine every day (or so) and have had no problems with reduced flow.

I did end up breaking a flange off the filter cartridge - rendering it useless. (Entirely my fault, I accidentally tried to screw it back together the wrong way.) Maybe could've been built more idiot-proof?

Either way, highly recommended! (If you aren't an idiot.)

Fast at first, then slow.


  • Light


  • Clogs
  • Hard to pump

I went on a 17-day stint on the Appalachian Trail with this filter. The first couple days it was amazingly fast and easy to use. Then it started to clog, even to the point where flow was reduced to 5 min/liter. It barely got me through the trip.

Source: bought it new
Price Paid: $100

I love my MSR microfilter! I have yet to have any problems with it, fills my bottles and my bags with ease and speed. I seriously could not be happier with it!

On a trip around Cottonwood Canyon it filtered for my wife and I around 20 gallons without a single problem. Backwashing, or reversing the pump to blow it out, can be a little problematic, but it really doesn't need it that often!

Price Paid: Gift

My first day out with this filter, I loved it. It was light, pumped fast and was compact. The honeymoon ended quickly though, as this filter plugs up faster than anything else I have ever used.

I have only used this filter in clean high Sierra water and followed the instructions on backflushing, but still found this filter USELESS after using it on a 6-night outing. Don't waste your money!!!

This is the first water filter I have ever owned. I bought the only one in town, and based on all the reviews I have read of other products, I would not trade.

I took the HyperFlow to the Flat Tops Wilderness Area for 4 days. It was so fast that after the first trip to the creek for water, everyone in camp thought I had just dipped the bottles, bladders and a pot into the creek and returned to camp. I did not try to test the 3 liters/minute pump rate for speed, but it only takes about 20 pumps to fill a nalgene bottle.

After several days the pump action got harder indicating it needed to be backflushed. After backflushing, it seemed to develop a pressure leak at the end of the stroke on the intake backflow valve side. I need to check the seating of that valve to make sure I got it back in place correctly, but the pump continued to work well.

This pump is easy to use, and comes in a nice compact little package with the instructions for operation and backflushing sewn neatly into the bag. I have not seen a replacement cartridge for it on the market yet, but I should not need one for a long time. Thanks, MSR.

Price Paid: $99

This filter made everyone on the trail jealous. It is soo fast and small. Greatest filter ever made. I have nothing else to say about it.

Price Paid: $80

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Price MSRP: $99.95
Current Retail: $119.95-$149.99
Historic Range: $69.95-$149.99
Reviewers Paid: $80.00-$100.00
Weight 7.4 oz / 209 g
Product Details from MSR »

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