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MSR Hyperflow Microfilter with Modified Cartridge Review

The MSR Hyperflow was previously reviewed in 2008, and was found to be light and convenient for crystal clear water, but it died very quickly in any other water. MSR acknowledged this problem and modified the cartridge to handle poorer water quality. The modified cartridge is tested here to see if there is an improvement.

Overall Rating: Below Average

As reported in our first Review, this is a neat little unit with a new form of filter, made of many fine micro-porous tubes. In addition, the design allows the unit to be back-flushed to remove any build-up of material on the surface of the filter. Field Testing of the first version showed that the filter blocked quickly when the water was less than crystal clear, and the back-flushing did not clear this problem. While the revised cartridge is slightly better, it still blocks quickly and backflushing still does not clear the problem.

About This Rating

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by Roger Caffin |

MSR Hyperflow Microfilter with Modified Cartridge Review - 1
Hyperflow kit, courtesy MSR.


The technical details of this filter were fully covered in the first version of this Review. Basically, the cartridge filter has a whole mass of fine 'micro-porous' tubes all bundled together. The tubes have tiny 0.2 micron holes in the walls for the water to flow through: holes are small enough to block the bugs. Water is pumped from the outside of the tubes into them, to emerge at the open end. MSR call this a 'Hollow Fiber Membrane'.

The problem with the first version, was that the walls of the tubes have a very limited area, and the fine holes were quickly blocked by the suspended matter found in any water which was not crystal clear. MSR eventually acknowledged this problem (after our first Review) and issued a statement which was added to our original review:

"We have identified a flow performance issue with some of the hollow fiber filter cartridges contained in MSR HyperFlow microfilters. The performance issue DOES NOT affect the product's ability to filter safe drinking water, but can be frustrating, as the flow rate of the filter may not perform to product specifications. The issue has been rectified, and all filter cartridges currently in production for the MSR HyperFlow microfilter perform to flow specifications. We have worked with our retailers to replace units they have in stock that may have this issue. Any consumer that is experiencing less-than-expected flow rates on this product right out of the box or after back flushing is urged to call us at 1.800.531.9531, and we will send a valid replacement filter cartridge at no charge if the original was manufactured prior to November 11, 2008. (Please have the filter element handy, as we will ask for the serial number for our records and manufacture date verification.)"

As the cartridge tested was dated well before November 11, we requested a replacement one. A few weeks later, a complete replacement filter kit was received. The contents were identical to the first kit received, except for the date code on the cartridge inside the pump. We do not know whether all requests will be dealt with like this.

This review is concerned with testing the new cartridge in a similar manner as before.


MSR claimed with the first kit that the outlet would fit into 'most water bottles'. This was tested with a 1.25 liter PET fizzy drink bottle (my standard free water bottle), and I could not get the outlet to fit. The instructions with the new kit made the same claim, so another attempt was made. This time, with a bit of 'persuasion', the outlet was fitted into the inside of the neck of the PET bottle.

MSR Hyperflow Microfilter with Modified Cartridge Review - 2
The Hyperflow fitted into the neck of a 1.25 liter PET bottle.

However, for reasons which will become apparent shortly, most of the testing was done with a silicone extension hose on the outlet, as shown here. This arrangement was also used in the first Review.

MSR Hyperflow Microfilter with Modified Cartridge Review - 3
The Hyperflow with an extension hose on the outlet.

Performance Testing

In the first Review, the author used water from the dam on his farm. This is a large dam and does have some ducks living on it. The water is not sparkling crystal clear mountain water, but it is not that bad. Until the author and his family (wife and two small children) got their house and a rainwater tank built on the farm, this was their drinking water.

MSR Hyperflow Microfilter with Modified Cartridge Review - 4
The water being filtered, before and after.

Here we have the dam water in a flat orange 20 liter basin. You can see a few little bits of 'stuff' at the bottom of the basin: this stuff is so large that the Hyperflow prefilter blocks it easily. Also shown to the right are two PET bottles of the water: one from the basin and one filtered. I would defy you to pick which is which. (The right hand one is from the filter.)

The water in the basin was allowed to settle before filtering started. Then, 8 liter of water was filtered with the MSR Hyperflow from the basin into water bottles of known volume. MSR recommends doing a backflush after 8 L, so this was then done. The MSR recommendation, which was followed, is for 10 strokes of backflushing using clean filtered water: about 0.5 L.


The first few liters of water were pumped with the filter between the author's hands, and the water did flow very quickly at the start. But after that, things deteriorated. The stages of testing are documented below with comments. Each filtering stage represents filling one 1.25 liter PET bottle with filtered water, except for the final (6th) stage which represents a bit over one PET bottle, to make up the full 8 liters. Each backflushing stage is one stroke (of the recommended 10 strokes).

While reading the results below, it may be worth noting that the packaging for the filter still claims that the filter will handle 'more than 3 liters per minute'. You may judge.


1. Easy pumping between hands - 1.5 seconds per full stroke, about 30 seconds/liter

2. Fairly easy pumping, as above

3. Getting a little harder

4. Getting a little harder

5. Switched to pumping vertically with one end on the ground, to get more force

6. Taking 3+ seconds for the downward stroke


1. It took ~30 seconds for the pump chamber to half-fill with water.

2. It still took ~30 seconds for the pump chamber to half-fill with water.

3. The ease of filling the pump chamber started to improve.

4. The ease of filling the pump chamber started to improve.

5. The ease of filling the pump chamber started to improve.

6. The ease of filling improved to the point where the chamber would fill to 9/10 full.

7. The ease of filling improved to the point where the chamber would fill to 9/10 full.

8. The ease of filling improved to the point where the chamber would fill to 9/10 full.

9. The ease of filling improved to the point where the chamber would fill to 9/10 full.

10. The ease of filling improved to the point where the chamber would fill to 9/10 full.

11. It took 10 seconds to 3/4 fill, and 15 seconds to fill to 9/10.

MSR Hyperflow Microfilter with Modified Cartridge Review - 5
My wife trying out the filter.


1. Despite the backflushing, the pumping was still hard: 2.5 - 3 seconds per downward stroke.

2. As above, after a brief attempt to pump 'between hands'.

3. Getting a little harder.

4. Gave my wife a go: she said the force was OK if she took 8 - 10 seconds per downwards stroke.

5. Tolerable downwards force needed at 6 - 7 seconds per stroke.

6. Tolerable downwards force needed at 6 - 7 seconds per stroke.


1. It took only 4 seconds for the pump chamber to 3/4 fill with water.

2. As above.

3. As above.

4. As above.

5. As above.

6. As above.

7. As above.

8. Possibly even slightly easier still, but not by much.

9. Possibly even slightly easier still, but not by much.


1. At the start, a 4 second stroke was managed, but this had become 6 seconds by the end.

2. As above.

MSR Hyperflow Microfilter with Modified Cartridge Review - 6
Pushing on (or downwards) with the testing.

You may notice in the photo here that I have taken off my thongs. That is because I was using one of them between the pump base and the ground. Without that buffering layer of foam, the bottom of the pump was steadily drilling into the soil. A lot of shoulder weight was being used to get the water through the filter. Anyhow, at this point my wife declared it was coffee time. I was getting a bit tired around the shoulders, so I willingly gave up. I could not see any point in continuing the testing: there would be no sudden miraculous improvement.

Other Observations

The inside of the filter cartridge was carefully inspected before and after each backflushing stage. Because I knew what to look for, I was able to see a very faint green/brown tinge on the surface of the filter tubes, but it was so faint that a casual user might not see it. It did seem that the same tinge was there before and after the backflushing cycles, meaning that the backflushing process was not able to remove it. This by itself calls into question the effectiveness of the backflushing process for handling typical organic 'stuff' in a water supply. That the backflushing process did not seem to have much effect on the pumping force anyhow, supports that doubt.

The first one or two bottle-fulls were pumped very easily. In fact, the first half of the first bottle was pumped so easily I did briefly wonder whether there was a filter cartridge there at all. The same ease of filtering has been reported with crystal clear mountain water by some users. It seems highly likely that if all the water supply contains is pure water and various bacteria and protozoa, then the filter would provide excellent service. It would be a fool who expected to encounter nothing but such perfectly clear water.

The first backflush cycle was, to my surprise, extremely difficult to get going, right from the very start. Yes, it was being done with filtered water. I do not believe that anything could have got into cartridge via the clean water to block up the inside of the micro-porous tubes. More startling was the discovery that the second backflush cycle was much easier to do. I have no explanation for this at all. However, as may be seen from the results above, backflushing did not seem to clear much of the muck (whatever it was) off the inlet face of the filter, despite my best efforts.

It could be argued that filtering 20 liter of water is hardly a good test of the filter. This would be true if the filter had worked well. But since the filter died almost at once - after the first couple of liters, I do not think further pumping would have proven anything I had not already discovered.

I mentioned in the first Review that I had also tried pumping this dam water through a Katadyn Hiker filter with no problems. I wrote there that the Hiker is widely regarded as the benchmark filter against which other filters are often compared. It uses a large pleated filter with a very long life, even on this sort of water. (That was tested.) It is my considered opinion that despite all the technological marvels embodied in the micro-porous tubing in the MSR Hyperflow, nothing substitutes for a multi-layer filter with a *big* surface area. The surface area on the MSR Hyperflow is just not big enough, and there is only one filter layer: the finest.


In the first Review, I wrote that the design of the MSR Hyperflow is nice; the filter is light, and that it works well with crystal clear water. All that is true, but many water supplies are not crystal clear, and the revised MSR Hyperflow cartridge still fails with less than perfect water, despite the changes.

The packaging still claims a flow rate of 'more than 3 liters per minute' I was struggling to get a flow rate of one tenth of this after filtering a few days worth of water. This claim is not credible.

We know that MSR is aware of this problem, is concerned about it, and has attempted to address it. The new cartridge is better than the old one, but it is still quite useless for any walker who has to deal with unknown and variable water supplies.







various plastics and polymers


various plastics and polymers

  Filter specification:

0.2 micron. Claimed to remove bacteria and protozoa to a degree which meets EPA requirements for water purification. This does not include viruses.

  Claimed filtering rate:

'more than 3 liters per minute'

  Measured filtering rate:

down to about 1 liter in 2 minutes, despite backflushing and force

  Filter life:

can be down to 20 L if water not crystal clear


~220 g (7.8 oz) for minimal kit of pump, full-length hose and inlet filter


Filter Kit: US$99.95
Replacement cartridge kit: US$39.95
Replacement prefilter: US$14.95
Maintenance kit: US$19.95

What's Good (from here and the previous review)

  • A fairly low weight
  • A neat design
  • Can be repeatedly backflushed
  • Useful inlet filter
  • Cartridge and inlet filters can be replaced
  • Removes bacteria and protozoa to EPA specifications

What's Not So Good (from here and the previous review)

  • Quickly blocks with any water which is not perfectly clear
  • Valve design can collapse under pressure
  • Nalge bottle connector is not ergonomic - and leaks
  • Needs an outlet hose added to the kit
  • Unsafe for winter use when freezing is possible
  • Silicone grease for the O-ring is not included with the kit
  • Does not remove viruses (most microfilters have this limitation)


"MSR Hyperflow Microfilter with Modified Cartridge Review," by Roger Caffin. (ISSN 1537-0364)., 2009-05-19 00:00:00-06.


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MSR Hyperflow Microfilter with Modified Cartridge Review
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Addie Bedford
(addiebedford) - MLife

Locale: Montana
MSR Hyperflow Microfilter with Modified Cartridge Review on 05/19/2009 16:48:40 MDT Print View

Companion forum thread to:

MSR Hyperflow Microfilter with Modified Cartridge Review

darren stephens
(darren5576) - F

Locale: Down Under
Thong on 05/20/2009 02:51:28 MDT Print View

G'Day Rodger
These blokes might think it a little strange that you used your 'thong' under the filter..

Edited by darren5576 on 05/20/2009 04:07:02 MDT.

Chris Chastain
(Thangfish) - F

Locale: S. Central NC, USA
MSR Hyperflow Microfilter with Modified Cartridge on 05/20/2009 03:14:23 MDT Print View


How much (clean, filtered) water would you estimate would be required to backflush as recommended by MSR?


Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: MSR Hyperflow Microfilter with Modified Cartridge on 05/20/2009 04:45:55 MDT Print View

Hi Chris

It's in the article:
"MSR recommends doing a backflush after 8 L, so this was then done. The MSR recommendation, which was followed, is for 10 strokes of backflushing using clean filtered water: about 0.5 L."


Matt Lutz
(citystuckhiker) - F

Locale: Midwest
Re: Re: MSR Hyperflow Microfilter with Modified Cartridge on 05/20/2009 06:10:56 MDT Print View

And I'm sticking with my Sweetwater. Thanks for the great review.

Are other review-collecting sites getting similar responses to the Hyperflow?

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: MSR Hyperflow Microfilter with Modified Cartridge on 05/20/2009 07:55:05 MDT Print View

Do any other sites have the inclination or capability to apply objective expertise to their testing?

BPL is unique in it's fanaticism, it's devotion, and skill in reviewing products. Other sites may be doing testing and other individuals may be doing "field testing",
but the majority of it is opinion and preference with very little substance.


Eric Hodges
(erichodges) - F
I used a Hyperflow on an 8 day trip... on 05/20/2009 13:48:14 MDT Print View

I had some problems with it being hard to pump after the first couple of days, but learned that if I pumped it slowly it still worked fine. This is also after quite a bit of abuse as I didn't back flush the filter for the first few days.

After 2 or 3 days, we (meaning me) started pumping only water that we needed right away for drinking or a meal and using purification tablets over night for drinking/cooking water for the next day's start. I like this method as the tablets are very light.

So, it's not perfect, has quirks and is a bit expensive, but it's light/small and if you don't try to force the pumping it works great.

Oh, and we were up in the Sierra and all the water was clear and nice, but not perfect as some streams were very shallow.

Note: just to be clear, I was getting really frustrated with this filter when I finally figured out that applying more force created more resistance...I then reduced the force/speed of the pumping and it worked well, but not as fast as the specs say.

Edited by erichodges on 05/20/2009 13:52:24 MDT.


Locale: Western Michigan
Date on Modified Cartridge on 05/20/2009 15:39:43 MDT Print View

QUESTION to Roger Caffin. I am curious to know the date on the MSR replacement cartridge you received. Presently I have a cartridge with a date of 112808 and I’m experiencing similar issues as you have.

Edited by KENLARSON on 05/20/2009 15:41:58 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Date on Modified Cartridge on 05/20/2009 17:30:03 MDT Print View

Hi Ken

Old one: '041808' meaning 18-April-2008
New one: '121008' meaning 10-December-2008


Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
The error is air on 05/20/2009 21:15:39 MDT Print View

I suspect that the “error was air” using an outdated backflush procedure BPL followed. The printed instructions included with my filter (4/08 version) have been updated in the video now shown on their site. My 4/08 manual states:

Backflushing the Filter Cartridge
Always perform backflushing in a controlled area to prevent the loss of small parts.
1. Collect ½ liter of filtered water into a clean MSR recommended container.
(See Tips.)
2. Remove Inlet Hose and unscrew Pump Inlet from Pump Cylinder. Do not pump
because trapped air will hamper operation. (See Troubleshooting.)
3. Reverse the Large Check Valve and reinstall it inside Pump Inlet.
4. Pull Pump Cylinder to end of stroke and turn until Piston locks.
Use cylinder to unscrew Piston from Filter Cartridge to reach Small Check
5. Reverse the Small Check Valve and reinstall it inside Piston.
6. Thread Pump Cylinder (with Piston and reversed valve) carefully onto the Filter
NOTE: Both tips of Large and Small Check Valves should point toward
the Pump Inlet
7. Thread Pump Inlet onto the Pump Cylinder. Again, do not pump air into pump.
(See Troubleshooting).
8. Connect container with filtered water to Outlet Adapter (or Outlet Nipple).
If using a hard bottle (Nalgene®), invert container to keep any air from
Outlet Nipple.
If using a flexible water system (MSR® Dromeday™ Bag with Quick Connect™ Bottle
Adapter), purge air from the bag before attaching Outlet Adapter.
If using a personal hydration system (Platypus® Big Zip SL™, CamelBak®), remove
Bite Valve, purge air from bag and Drink Tube, and attach Drink Tube directly onto
Outlet Nipple.
9. Pump 10+ full strokes of filtered water to flush Filter Cartridge.
Wait for Pump Cylinder to fill with water during each stroke.
When backflushing is completed, disassemble pump and reinstall the Large and Small
Check Valves in their original, forward flow position. Dry pump assembly and then
reassemble. CAUTION: Protect Filter Cartridge from accidental drops, which may
damage the filter.

In contrast to these printed instructions, what I have found to work best (note steps 4, 10, & 13) and what the current MSR instructional video now shows is:


Secondarily, the most recent review has a picture with the caption, "Pushing on (or downwards) with the testing" and the original review has a picture with the caption, "The pumping action"... they also indicate air introduction to the outer surface of the hollow fibers which may also reduce the filter’s effectiveness.

The following 2007 independent research report entitled, “Unstable filtration behavior with submerged hollow fiber membranes” was authored in part by UNESCO Center for Membrane Science and Technology, Chemical Sciences and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.

It says in part, “…The formation of these stagnant bubbles is attributed to some ‘dry’ points existing on the internal surface of the hollow fiber membrane. It appears that these ‘dry’ points cause significant and unstable local resistances for the permeate flow inside the fiber lumen. For a fixed average flux the high local resistance results in increased suction pressure in the lumen region downstream of the ‘dry point’ and this shifts an additional flux load to this region. The resultant maldistribution of local fluxes caused by abnormal local flow resistances can markedly affect the filtration behavior of the hollow fiber membrane. Interestingly the effect was not observed for all fibers and appears to require local ‘dry point’ existence within the lumen.

Edited by richard295 on 05/20/2009 21:39:22 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: The error is air on 05/21/2009 02:17:04 MDT Print View

It's an interesting theory, but having fairly carefully reviewed my notes I don't think so.

I did find that starting the backflushing the first time was slow for the first few strokes, and I am quite willing to accept that air bubbles may have been the problem. Interesting, and thanks for pointing this out. But I tghink they were flushed away after several strokes.

What is revealing is the first filtering cycle, where there was a very noticeable deterioration in ease of pumping as I progressed from bottle 1 to bottle 6. (Bottles are 1.25 L each.) I cannot see that air bubbles could possibly account for this change in resistance while filtering. I was getting an increase in resistance before any backflushing was done.

The second filtering cycle (after the first backflushing) showed the same steady deterioration in ease of pumping as I went from bottle 1 to bottle 6. Again, this is consistent with a steady blocking of the fine pores, not with air bubbles.

I noted:
"Because I knew what to look for, I was able to see a very faint green/brown tinge on the surface of the filter tubes, but it was so faint that a casual user might not see it. It did seem that the same tinge was there before and after the backflushing cycles, meaning that the backflushing process was not able to remove it. This by itself calls into question the effectiveness of the backflushing process for handling typical organic 'stuff' in a water supply."

I do not question the effectiveness of the filter at handling particles at the typical bacteria size. I imagine that if you only ever filtered really clear water the Hyperflow would do a good job. The problem is that the whole design allows typical gloopy organic particles to block up the surface of the tubes, and backflushing does not get them out of the pores.

If MSR put a 15 - 20 micron paper pre-filter before the tubes to handle the gloopy stuff it might make a world of difference - but you would have to change the paper every day.

Beautiful technology, but only for clear water imho.


Eric Brewer
(enbrewer) - M
My experience matches Roger's on 05/21/2009 08:01:29 MDT Print View

Last fall, in the White Mountains, we used the Hyperflow (pumping water for a family of 4) with pretty similar results. First couple of liters went fine, then it all went steadily downhill. Backflushing helped only minimally. By the end of the 5th day, I was getting pretty exasperated. But backflushing seemed to be different on different days, despite following the same procedure each time. Sometimes it helped more than others.

Returning home, I backflushed MANY, MANY times (lost count) and got it back to almost as good as new. But I'm not sure I'll take it on a trip longer than a weekend.

Contrast this with my Sweetwater, which is not nearly so compact, but always works flawlessly and has a great leverage system so pumping never requires excessive effort.

Richard Nisley
(richard295) - M

Locale: San Francisco Bay Area
Re: Re: The error is air on 05/21/2009 09:54:46 MDT Print View


Thank you for your response. I agree "error is air" is only a theory that attempts to account for different people's testing experiences. I also perceive increased pumping resistance proportional to both the water clarity and volume processed. I, like you, agree that "this is consistent with a steady blocking of the fine pores". We differ in the conclusion that as a result of the above the Hyperflow is most appropriate for water without "gloopy organic particles" which plug it up. I concluded that clear water is most easily treated by chemical means; it is only opaque water that requires the weight and the effort of a field-cleanable filter such as the Hyperflow, WaterWorks, Katadyn, etc.

I own two other brands of field cleanable filters: a WaterWorks EX Microfilter and a Katadyn Pocket Filter. I only accept the weight and effort of these mechanical filters when I know I will have to frequently treat opaque water for long periods (for example glacial silt rivers or muddy rivers). All three field cleanable filters exhibit a similar degradation pattern from blocking of the fine pores.

Both the WaterWorks and the Katadyn require that I periodically open up the filter and use a stiff brush to scrape away the outer sheath of the ceramic labyrinth element. With the Waterworks and Katadyn, the cleaning procedure always restores the original pumping efficiency. By contrast, the Hyperflow's original pumping efficiency is not restored unless I follow the modified protocol shown under the column entitled Nisley.

In the field, I use the Hyperflow in both gravity feed mode and manual pump mode. The BA Pumphouse gravity water source is 6L and takes approximately 17 minutes with pristine water and only a few more minutes for farm pond quality water. After a farm pond gravity feed operation, the filter definitely requires backflushing. My experience has been that the backflush operation procedure used is the primary determinate of subsequent manual pump pressure required.

Edited by richard295 on 05/21/2009 10:01:23 MDT.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: The error is air on 05/21/2009 16:18:16 MDT Print View

Hi Richard

More backflushing needed? Maybe. Mind you, the Hiker remains the Gold Standard for filters imho.

However, I have switched to the lighter Steripen Adventurer which treats protozoa, bacteria AND viruses, fast. Having copped it REAL bad from viruses once, and also Giardia twice, I am happier that way.

My personal opinion is that UV can/will replace both chemicals and filters, especially once the UV LEDs get onto the market at a reasonable price.


Richard Schnetzer
(RCS) - F

Locale: Southern California
Similar problems with MSR filter replacement on 05/26/2009 16:13:28 MDT Print View

I can report similar issues to the updated review by Roger. Although MSR replaced my original filter with a new one at no cost (kudo to MSR for their effort), on a recent backpack I found that the pump output was severely restricted, would work OK if I went very sloooowly, but in no way gives the result that MSR advertises re: flow/output.

Zack Freije
(oldskool) - F

Locale: Ohio
Re: MSR filter replacement on 06/13/2010 02:05:43 MDT Print View

I was sad to see this review. I recently hiked with a friend who has been using this filter for some time in the backcountry with no issues or complaints. She did not have the backflushing issues, reduced flow, or need to change the filters so quickly. She originally had a military version and loved it so much she switched to this one when she couldn't find a civilian source for filter replacement.

I tested this filter on our last hike and it had an amazing rate of flow, the water tasted great, and we dropped the filter element into very shallow, mostly muddy water, with no issues.

I was set to purchase this to replace my current steripen setup, but now I have concerns.

I wonder why she could have so few complaints compared to so many here.

Matthew Swierkowski
(Berserker) - F

Locale: Southeast
Good review, I've had similar issues on 06/23/2010 11:22:25 MDT Print View

I've posted some of my experiences with the Hyperflow on BPL and another site or two. Following is the history of my Hyperflow. I bought it in 2008 when it first came out on the market, and it worked well for a few days then became almost impossible to pump. MSR acknowledged that there was an issue with the first batch of cartridges (as was documented in the review), and replaced mine at no charge. The new one they sent me went about the same way as the first one where it worked for several days then became really hard to pump. So I sent that one back, and they sent me yet another cartridge. The newest cartridge was first used on the most recent trip I took (part of the AT in Vermont), and it clogged up in about 3 days. My buddy, who also has a Hyperflow and has not previously had issues with his, had his clog up after about 3 days on the same trip. It is notable that we both filtered dirty water from multiple sources, in particular we had to filter out of one of the lakes (Griffith).

The filters are usable if one pumps very slowly, but then its only claim to fame is being a few ounces less than its competitors. I appreciate MSR's customer service, but I've pretty much given up on the filter itself. I think I'm going back to my Katadyn Hiker, my Sweetwater or I may even try the one treatment technology I haven't yet tried...UV.

Edited by Berserker on 06/23/2010 11:24:05 MDT.