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Reviews > Water Treatment > Filters > MSR Hyperflow Filter > Test Report by David Wilkes

Test series by David Wilkes

MSR Hyperflow Filter

Initial Report - March 13, 2009
Field Report - May 26 2009
Long Term Report - July 28 2009

David Wilkes


Tester Information

Name: David Wilkes
Age: 42
Location: Yakima Washington USA
Gender: M
Height: 5'11" (1.80 m)
Weight: 197 lb (89.40 kg)


I started backpacking in 1995 when I moved to Washington State. Since then, I have backpacked in all seasons and conditions. I have usually only managed time for 1-3 trips a year averaging 2-5 days, and as many day hikes as I can. I am currently getting into condition to summit some of the higher peaks in Washington, Oregon, and California. I prefer trips on rugged trails with plenty of elevation gain. While I continuously strive to lighten my load, comfort and safety are most important to me. My current pack is around 30 lbs (14 kg), not including consumables.

Product Information


Mountain Safety Research

Year of Manufacture:


Manufacturer’s Website:


US $99.95
Listed Weight: Kit 10.2 oz. / 289 g.
Pump + Pre-Filter 7.4 oz / 210 g
Measured Weight: Kit 10.8 oz. / 306 g.
Pump + Pre-Filter 8.1 oz / 232 g
Dimensions (listed): 7 x 3.5 in. 17.8 x 8.3 cm 
Cartridge Life: Up to 1,000 liters (depending on conditions) Per the manufacturer
Flow Rate:

3.0 liters per min (depending on filter condition, and water quality) Per the manufacturer

Product Images
Image courtesy of Mountain Safety Research

Product Description:
The MSR Hyperflow is the latest water filter in MSR’s “Fast & Light” series of products. It operates similar to a small bicycle tire pump and utilizes what the MSR calls Hollow Fiber Technology (0.2 Micron pore size). It includes a pre-filter, hose, and quick connect bottle adapter. It is touted as having a high flow rate (1 L in 20 strokes), and field maintainable without tools (including the ability to backflush the filter in the event of clogging) .

Initial Report

My measurement of the weight was just slightly above the manufacturer’s specifications, however I weighed the pump after using it, and despite trying to remove all the water from the pump, I suspect there is still some residual water in the pump that could account for some of the discrepancy in the weight.
The Hyperflow operates similar to a small bicycle tire pump and utilizes what the MSR calls Hollow Fiber Technology (0.2 Micron pore size). It includes a pre-filter, hose, and quick connect bottle adapter. It is touted as having a high flow rate (1 L in 20 strokes), and field maintainable (including the ability to back flush the filter in the event of clogging) without tools.
Close up of the filter cartridge
Close up of the filter cartridge ends
I did some research on line in preparation for this test. I was curious as to what makes this filter so different from others on the market. I was unable to find much information regarding the “Hollow Fiber” technology on the website, so I did some research on-line, and reached out to MSR to see if they had some additional information they could send me. What I found was fascinating (to me anyway). Apparently, the technology is derived from filters used in dialysis to filter blood, wastewater treatment plants, and laboratories. The filters are strands of hollow fibers made from a porous material. The following is from a web link that MSR sent me in response to my request for additional information on the filter:  
“The concept starts with a bundle of hollow fibers that are “glued” in place. The water is filtered as it passes through the micro porous walls of these small tubes and comes out down the center of each one. The benefits to this media are that you can fit a substantial amount of filtration surface area in a much smaller area, resulting in much higher flow rates and a much lighter, more compact system.”
The pores in the fibers are small enough (0.2 Micron) to block sediment, bacteria and protozoa (but not viruses) that may be in the water.
The filter itself is different from all other filters I have seen. As stated above, it resembles a small bicycle tire pump, right down to the quick connector extending out the side of the top end of the filter. The filter takes in water through a hose connected between the bottom of the filter the pre-filter. The pre-filter is also unlike any I have seen. It is a flat rectangular pad like device that takes in water from the bottom and attaches to the filter hose on the top. The idea is that the filter floats on top of the water where the least amount of sediment is likely to be. This design also makes it possible to draw water from very shallow sources (the manufacturer mentions being able to “suck water off of a rock”). The pre-filter is flexible and is designed to be wrapped around the pump, after winding the inlet tubing around the filter, and is held in place by wrapping the pre-filter closure strap (hook and loop type strap attached to the pre-filter) around the pump. When wrapped up for storage the pump assembly makes a small neat package.
In addition to the above listed items, the pump came with a handy little storage sack. The sack has one zippered mesh pocket that fits the pump, pre-filter, hose, and quick connect cap on one side. There is also a second zippered pouch on the other side that I expect to use to store the instructions and maybe other small items like drink mix.
The pump comes with a ‘clean side cover’ that covers the pump outlet adapter. This cap comes off completely when not in use, so losing it is a possibility (especially for me since I have been known to lose small items like this). The water exits the pump out of a port on the side of the top of the pump. The output of the pump is designed so it can be connected to the drink tube of many common hydration systems or inserted into the opening of containers with smaller openings like Platypus or common disposable plastic water bottles. In addition, the pump is designed to be quickly connected to the included bottle adapter. The bottle adapter is intended to replace the fill cap of MSR and other hydration bladders, and provides a quick connection to the pump. The quick connect bottle adapter fits my MSR hydration bladder as well as, a generic hydration bladder I have, and the large opening water bottles I have (I tried it on bottles from 3 different manufacturers and they all fit securely with no leaks). The bottle adapter has a quick connect opening and cover. I tried attaching the pump output to a standard disposable water bottle, it fit snugly and securely.

The pump comes with an illustrated instruction book (actually 10, in different languages), covering the common usage of the filter, the various setups, along with maintenance instructions, specifications and tips on using the filter with various containers. This is the same instructions available for down load from their web site. In addition to the instruction manual and “Filter Test Guide”, stitched inside of the storage pouch is a water resistant sheet showing the assembly of the pump for normal use on one side and the configuration of the valves for back flushing on the other. This sheet is perforated so it can be detached from the pouch if desired.
In addition, a separate “Filter Test Guide” sheet explains the recommended process to test the pump to verify the filter media’s integrity. If the filter does not pass this test, the instructions state to replace the cartridge.
The filter documentation mentions a warning I found notable for a piece of backpacking gear. It states never to store the filter cartridge in temperatures below freezing, as freezing will permanently damage the filter fibers. My research into hollow fiber filter media suggests that this is a common problem for this type of filter. MSR recommends storing the filter where it is unlikely to freeze if freezing temperatures are anticipated (e.g. in the hikers tent or if necessary in the sleeping bag).

All parts of the pump as well as the accessories seem to be of the highest quality and I could find no indications of any defects or likely failure points. Initial assembly and basic operation were easy to figure out (prior to reading the instructions). I tested the pump by pumping clean drinking water from a pot into a 1L (32 oz) water bottle. The pump required a bit more effort to operate than I expected and filled my bottle in about 20 strokes. The quick disconnect cap fit securely on all the bottles I tried it on, and the pump attached to the cap easily and securely. After reading the instructions, the back flush procedure was quite easy to understand and perform. The procedure for testing the pump for damage was a little less intuitive, but after performing it once, I expect I should be able to perform it in the field without the instructions if necessary.

Image of pump packed for storage
Packed for storage and laying on top of the instructions

Image of the pump and accessories
The Entire Kit

Field Report

 Field Report Usage Summary:
* Day hike – Umptanum Creek Washington – Pumped 2.5 L (85 oz) w/flush
* Backpack (one night) Bear Canyon Washington – Pumped 4 L (135 oz) w/o flush
* Mountain Bike Ride (12mi / 19 km) – Cowiche Canyon – Pumped 2 L (64 oz) [cloudy tan water] w/o flush
* Backpack Bishop California (one overnight & one day hike) – Pumped 2L w/flush
* Backpack (3 nights) Alpine Lakes Wilderness Washington – Pumped 5.5 L (186 oz) w/o flush

Pump in useI took the HyperFlow on a day hike up Umptanum creek. The creek was quite brown from the spring runoff. I did a bit of exploring around some of the side canyons and found a small stream that was running clear. It was a bit shallow with a muddy bottom. With the pre-filter configuration of my old pump (weighted foam) I would hesitate to pump from this stream since the only way to get it fully submerged would be to have it in contact with the bottom and hence sucking up the mud. Recalling a comment from the manufacturer about the pump being able to suck water off a rock I found a flat rock submerged just enough so that when I placed the HyperFlow’s pre-filter it was mostly submerged. I filled my 0.5 L (16 oz) water bottle by attaching the pump to the quick connect lid. I also filled my 2 L (64 oz) hydration bladder by attaching the pump directly to the drink tube.
While backpacking in Bear Canyon I filtered a total of 4 L (135 oz) from a clear running stream without back flushing. I experienced some difficulty in keeping the pre-filter facing downward in the moving water. I experimented with wrapping the hook/loop straps across the back of the pre-filter, but I don’t think that helped any.
I took my mountain bike up Cowichi Canyon (an old rail line converted to a hiking trail) and intentionally did not take any water. At the top of the canyon I filled up my 2 L (64 oz) hydration pouch. The water was light brown and cloudy. I did not back flush.

Rock attached to pre-filterOn my trip to Bishop, California, I attempted to hike from Sabrina Lake to Lake George but was stopped short by deep wet snow (I brought the wrong boots for that). I camped at around 10000’ and filled my 2 L (64 oz) hydration bladder from the very clear running stream. It seemed like it might be harder to pump than it was before so I back flushed the pump to see if that would make a difference. It did not. So I figured it was going from 800’ (244 m) to over 10000' (3000 m) in 24hrs that made things just seem harder.
I hiked into Cooper Lake in the Alpine Lakes Wilderness intending to continue on to Pete lake but was stopped due to deep wet snow that I was not prepared for. Instead I spent the weekend camped at Cooper lake. While there I pumped a total of 5.5 L (186 oz) of water from the very clear lake. I continued to have difficulty in keeping the pre filter face down in the water. I finally used the hook & loop straps to attach a rock to the back of the pre filter in order to keep it under the water and thereby not suck a mix of water and air. This worked quite well.

The HyperFlow is a very small light pump that filters quite a bit of water quickly. It requires a bit of force to use, so I don’t think I would want to use it to filter all the water for a large group. But for 1-3 people I think it would work quite well.
I have used the filter to fill my hydration bladder through the drinking tube, fill my Nalgene water bottle using the quick connect bottle adapter and I have filled ordinary disposable water bottles, with no difficulties. Connecting and disconnecting the filter to these was quick, easy, and reliable.
The pre-filter is a neat design but I have had difficulties in keeping it face down in both moving and still water. Attaching a rock to the back was quite effective and I intend to continue to do that unless there is a risk of picking up too much mud and silt from the bottom of the water source. While it works when the pre-filter is not fully submerged or sitting flat on top of the water it sometimes picks up quite a bit of air along with the water requiring more time and pumping to filter the same amount of water. The manufacturers claim that it can suck water off a rock is not the exaggeration I expected it would be, as evidenced by my doing just that.
The thing that has surprised me the most is how much I like the quick connect bottle adapter. I have found I like having this lid on my Nalgene bottle, the quick connect opening is very convenient to drink out of.
So far I am quite happy with the size, weight, and performance of the HyperFlow. My only outstanding question about the product is its longevity. I have used my old filter for many years with no difficulties, but it is now packed away with the gear I no longer use until such time at the HyperFlow fails (if ever).
Pump attached to quick connect bottle adapterPump attached to disposable water bottle

Long Term Report

July 28 2009
* Day hike Mt Rainer National park (carried but did not use)
* Day hike Umptanum Falls (pumped 2L without back flush)
* Backpack trip to Umptanum Falls (pumped 4L without back flush)
* Canoe trip on Rimrock Lake (pumped 1L back flushed after returning home)
* Day hike Pleasant Valley, Washington Cascaides (pumped 1.5L without backflush)

I took the pump on my daughter’s 6th grade field trip. I ended up not using the pump on this trip due to not being able to find safe access to the river near where we stopped for lunch.
I took a quick hike to check out a possible camp for my 6 year old's first backpack trip. I wanted to go quick and light, so I took minimal gear. I decided to take an empty water bottle and the Hyperflow to save weight and get some water when I stopped at the campsite I was checking out. This worked very nicely. It was a pleasure to speed down the trail with virtually no weight encumbering me. I stopped to check out where I planned on camping and filed my water bottle from the stream. The water along the way was running very slowly and in the places where it pooled looked stagnant and rather unpleasant. Under different conditions I would probably have avoided drinking from this even after filtering it, but between the fact that I am testing a filter and had such a short quick trip back to my vehicle I decided to risk it. The water was warm and tasted a bit like dirt, but not unpleasant. I filtered and drank half a liter, with no problem. The pump's lightweight and quick/easy setup, combined with its high rate of flow makes this an attractive option for when I want to cut down on the weight I carry and know there is a reliable water source available.
Hyperflow vs. nasty gray waterOn my backpacking trip to Umptanum falls with my daughter I had some concerns about the quality of the water available. While there were fish living in the biggest pond, the water in many spots was a nasty looking dark gray (maybe a bit worse than on my previous trip) and I even noticed the jawbone of an animal in the water just upstream from where we camped. I made it a point to bring enough water with me for my daughter to drink and only used the filtered water from the stream for cooking and for drinking myself. I also made it a point to only collect water from above the spot with the animal remains (the ones I could see anyway). As in my previous trip the water was not the best tasting, but I experienced no health problems. Jaw bone in water
During this trip I noticed that the pump seems to leak just slightly. While pumping I noticed a few drips of water was coming from in-between the two sections of the pump. While this is not a problem in and of itself it makes me wonder about the long term durability of the product. Also during this trip, I realized the one non-intuitive step in using the product (at least for me) is the test to see if the filter media has been damaged. I realized this is not part of the instructions that are attached in the inside of the pump carrying pouch, and I forgot that I had the full instructions with me.

I used the pump during a day trip where my daughters and I spent the day paddling our canoe around Rimrock Lake. The lake water was only slightly cloudy and warm enough to swim in. Operating the pump from the canoe was very easy. I simply dropped the pre-filter into the water next to me, attached the pump to my water bottle and pumped. Again the pre-filter floated on the top of the water only partially submerged. After returning from this trip I thought again about how the pump leaked slightly during the previous trip so I looked up and performed the Integrity Check process. The filter did not pass. While holding the pump for the recommended 4 seconds I could hear air leaking into the pump chamber and when I released it, it only moved back slightly, not the ‘snap back’ that the instructions describe (I tried this out while going over the product in preparation for the Initial Report and it worked then). Since I know I have not dropped the pump and have not let it freeze, I am surprised at this failure. I have tried holding the pump to my ear and the leak sounds like it is coming from the output end of the pump. I don’t know how to figure out if the problem is with the filter media or the seal. Before contacting the manufacturer I decided to go over the process again to be sure I had not missed anything and maybe better identify the problem. I started by going to the MSR Water Treatment FAQ (Frequently Asked Questions) and found the following:

“In preparation you need to make sure that your filter is fully wetted out. This means that you should have pumped several liters of water before performing this test. Generally your Filter Cartridge will not dry much during storage, so as long as you have used the pumps a few times, you should be in good shape.”
After reading this I tried pumping some water through the filter and back flushing it before doing the integrity test again. This time it passed! Since I had just used the pump the day before, I think the “will not dry much during storage, so as long as you have used the pumps a few times, you should be in good shape.” may be a bit misleading. My recommendation would be to be sure you only perform this test immediately after pumping water through the filter.
I used the pump on one final trip, a family day hike with the Cascadians in Pleasant Valley. It was a short hike where I pumped about 1.5l out of a small stream to refill our water.

I continue to struggle with getting the pre-filter to remain in the water, and have given up trying to get it to sit on top of the water facing down as it is intended. Every time I use it, it ends up only partially submerged and at an angle. Attaching a rock to the pre-filter has been effective, but I don’t like to do that if this will cause the pre-filter to come in contact with the muddy bottom of the water source. The pre-filter seems like a good idea, but just does not seem to work as intended. At the conclusion of this test series, I am considering trying the pre-filter/float from my old pump with the Hyperflow to see how well they function together.

The Hyperflow’s small size, light weight, and speed along with the ability to back flush in the field are real advantages. Sometimes with my old pump I would have an internal debate as to if I was really thirsty enough to pull the pump out and filter water. With the MSR I have been filling my water containers more often and as a result despite often carrying less water than I normally would I have remained better hydrated. The pump's only disadvantages are the force needed to operate it and the poor performance of the pre-filter. Aside from the pre-filter, the pump works as advertised  and has performed admirably. Losing one of the small parts (outlet cover or valves) could be a problem if I am not careful, and so carrying spare valves might be a good idea. Overall I am very happy and impressed with the Hyperflow, and would recommend it to friends and family.

This concludes my report. I would like to thank the folks at Cascade Designs, inc. and for the opportunity to test this fine product..


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