I filtered for myself and allowed others to use my HyperFlow over a week in Yellowstone NP. A friend did the same with his HyperFlow, and neither one of us had any problems.

I benefited from a suggestion, though. I put an MSR SiltStopper II between the HyperFlow's pre-filter and main pump, and it definitely cut down on the need to backflush the HyperFlow. I'd guess my friend (without the SiltStopper) backflushed at least twice as much as I did during the trip. There's even enough room in the HyperFlow's included pouch to keep the pre-filter & SiltStopper in the mesh side, and the pump in the other.

I always take some Katadyn Micropur tabs as a back up, but I have no complaints with the HyperFlow.

This is a great filter and it pumps very quickly the only thing i worry about is how big the pores must be to allow so much water to go through

The bad reviewers mostly are saying how good it worked at first, how fast and effective it is. But then say the next day how slow it is..I wonder if they read the directions or if theirs really were defective. This small filter is suppose to be 'back flushed' every 8 liters, that's very often, especially these people saying they used it for groups or 3-12. this shows how to do it, for those you already own and haven't read the directions properly.

http://www.youtube.com/watch?v=hUBZTfPUDP8

for those whose really 'sucks' that's a bummer.

A group of 7 of us went into the Sierra on a 3 day trip. We were using my old Pur filter which has been a trusty unit for 10 years. But then my friend (who doesn't backpack much) pulled this thing out of her pack. I got first crack at using it, and I was blown away. It pumped my platypus full in less than 60 seconds. I couldn't believe how small this thing is and how smart the design is. However, my opinion changed later that night when I borrowed it again, and could barely get it to function. Instead of seconds, it took 10+ minutes to pump the same amount of water. Granted, I don't know what happened in the intervening hours, but I don't think the filter was misused by anyone. All the water we were filtering was very clean and clear. The next morning I took it apart and couldn't find anything dirty, clogged or otherwise gummed up. Still, it refused to pump water at any kind of reasonable rate. At that point, it was essentially a tiny workout device.

Disclaimer: Don't buy this filter if you plan to use it primarily for more than two people.

I use this on solo backpacking trips and it works great as long as you know how to use it. The pump must be backflushed FREQUENTLY in order for it to work well consistently. A lot of people give this filter a bad rap but they have most likely had bad experiences because they got the wrong filter for the job. I love my microfilter. It is light and pumps really quickly (although you do have to take into consideration all the time you must spend maintaining the filter). My only complaint is that screw top for nalgenes/hydromedary bags leaks a bit. As long as you hold the nalgene or hydromedary completely upright while pumping into it through the accessory top you should not have a problem. However, this is much more difficult to pull off with a hydromedary bag.

I had trouble with this one on the trail, even after following directions. At first it did filter quite fast, but did require some effort. At exactly 8L, this filter slowed to a dribble, obviously indicating a backflush. After fussing to reverse the valves, the backflush procedure didn't work as well as I would have hoped. It was still difficult to pump water through, and even a long back flushing would not improve it.

In addition, the intake side of the pump would often come loose during pumping, spraying water everywhere. The pre-filter float also wouldn't stay submerged enough or face down effectively in the water.

I ended up going for an extra ounce or two with the Autoflow gravity filter, and have been so much happier. No pumping, simplistic back flushing, water storage, backcountry shower, etc.

After filtering 8 liters of water from a clear mountain stream this thing clogged. No amount of backwashing per the directions could fully restore it. It never pumped 3 liters per minute as claimed. The best thing I can say is that I got a good bicep workout trying to push the plunger down. Someone else in my party carried a Katadyn Vario which functioned perfectly. This is junk...don't waste your money.

This filter did NOT live up to expectations. The float end wouldn't stay face down in the water. Even worse, the filter cartridge clogged very easily when the water wasn't perfectly clear (e.g., when there's any presence of algae). The only way to backflush was to waste up to 1 liter of water for every 8 liters you pump -- you can't clean the filter directly like other MSR ceramic filters. Definitely not worth the extra money. Go with a proven and cheaper MSR pump instead (such as the Miniworks EX).

Worked great in sink, terrible on Vancouver Island's North Coast Trail and later (with a new one) on Vancouver Island's Strathcona Park. on the NCT, murky creek water clogged the filter and backflushing on trail would not improve pumping speed/effort within 60% of original levels. Thorough backflushing in sink at home returned filter to 80% of original pumping speed/effort. Replaced with a new one and took to the alpine (nice clean water) and had the same problems. Backflushing this time on the trail and extensively at home only replaced the unit to 60% of original values. Would not recommend this. IMO it's job should be to filter water for you, no matter where you are. It is amazingly light and small though (and originally pumped wicked fast)

Used it on a 10 day trek in Ladakh where the water was very clear. The pump worked great and really fast for the first 10 liters or so, after that it went slower and slower, even with regular back flushing. I think I got about 50 liters out of it when no back flushing could restore it to a usable state. As said the water was already clear to begin with so this was quite disappointing. Fortunately we could still boil the water and there were several springs on the way that proved safe. Fortunately I got full refund. Next time one I'll get one of the ceramic filters, they are harder pump and slower, but at least the keep working and can be cleaned more easily.

I have owned the hyperflow for a close to two months now and I think it's awesome. I'm always a little skeptical of new filters but I've pumped some sketchy looking water and I didn't get sick at all. I was trying to convince my hiking partner to take water straight from the source but he refused. This filter is way faster than my old sweetwater. The only problem I've been having is not realizing my camel back was full it popped off my drinking tube and sprayed all over. Great product from MSR.

I own one of the first of these released. I thought, "great... light, effective, fast. I'm so cool and my butt is covered." But..... It is as everyone says...starts out really fast and easy, then really goes downhill quickly Anyhow, I just discovered, purely by chance (gee, thanks MSR) that all of you who bought before 02/09 can contact MSR for a new filter cartridge. The info is on their homepage but the number is:1-800-531-9531. We'll see if that solves the problem If it can live up to what it once was and the entire reason I bought it, It is a nice little unit. Just in case, I'll carry some chlorine tablets for the summer.

New cartridges to the masses.

When I bought this filter a few weeks ago, I tried it out at a stream near my house and it was amazing. However, it became less amazing about six hours into an eight day camping trip. At first it was just difficult and slow, but later the flow reduced to a trickle. I was backflushing every 6-8 liters (which is really easy and not much hassle at all once you've done it a few times - just make sure you have a nalgene or platypus. Klean Kanteen also makes an attachement which should work.) Anyways, we ended up boiling water for the last four days. When I got back, I called MSR about it. They asked for my name, address, and the serial number, and then sent one out right away. The call took about two minutes. Now my hyperflow is working perfectly. If you want to be on the safe side, you might consider buying this from a smaller camping store, because they would have the most current ones (having to restock more often). If you decide to buy it on backcountry, just make sure to call MSR and check that serial number. It really is a great little filter; It comes in a double sided carrying pouch with simple instructions. I have done dayhikes with just this - no water bottle - but that was mostly for the fun of it. Like having a water fountain in your pocket.

I recently spent 5 days at lakes above 10,000 in the Sierras. I pumped mostly in running streams. The filter clogs really fast. Backflushing doesn't take too long but it never recovered and was a pain to pump. I'll stick with my MSR miniworks. It's worth the extra 9 oz or so.

I am not sure where and how some of the reviewers used this filter, or why they are writing such negative reviews. I have been hiking and using filters now for 15+ years (Katadyn, Sweetwater - and they also work fine, but slower). Just used this one again on 7 day trip up north (Fort Nelson area)for group of 3. Water was mostly from creeks of various clarity. No problem with the float end at all, actually it works great! We had 3 filters, but after the first use we only use HyperFlow. My partners wanted to buy it from me right there! Easy to use, very light, fastest flow by far when compared to anything comparable. All filters plug up and slow down in silty water, so what? It is so easy to back flush (best to do right after watering up and it takes me about one minute). True, I have not use it to try to pump water from a puddle so far, but I had only do it once in last 10 years. I am sure it can be done, but it may take a little longer to get your 4-6 liters done. For now I say if you like lite and fast, buy it, you'll love it! Excellent gear!

I used it for awhile and didn't have the problems others had with flow rate. The only time I needed to backflush it was when I used it in muddy water.

The problem I had with it and the reason I returned it was because of the freezing issue. I wanted something I could use all year. I understand you can't use it if it's frozen but I didn't want a filter that when it does freeze I need to test it and possibly buy a new filter.

I exchanged it for the Sweetwater filter. No freezing issues and no need to sleep with it in my sleeping bag and keep inside my jacket all day.

I've been backpacking and climbing for over 20 years (I hate saying that...) and this is the best thing I've ever used to filter water. I'd been using it off and on on shorter trips in the Cascades and was blown away - but that's easy for most filters to accomplish. So, the proof was to be found on an 8-day trip in the High Sierras and I even bought a spare filter cartridge just in case. My research had turned up some folks griping about clogging etc. but I can only imagine that they were doing something wrong or filtering REALLY silty water. True - it does slow down if you are filtering really silty water. I noticed the difference between a glacial-fed lake and some others that were lower - but we backflushed as recommended (every eight liters, or about once every other day for two people) and had no problem whatsoever. And for those worrying that backflushing that much is too much - think again. You'll never even consider going back to another filter after realizing how much easier the Hyperflow is. We got used to backflushing right as we finished filtering and it only added about 1-2 minutes - Far less than the time saved by the Hyperflow's speed and the overall ease of pumping more than makes up for any inconvenience you thought you might have felt. We even started to routinely do the filter test at the same time because it was so easy to do in the process. I will say that I wouldn't use it in direct glacial meltwater and I have no idea how it would do in the Canyonlands or other places with really murky water, but I'm guessing it might not be the best choice there. However, if you want to get a superlight, and really small filter for taking on alpine trips or anywhere the water is pretty clear, I can't imagine a better set-up. I even take it on day hikes and car-to-car alpine climbs now and pump as I go. It beats lugging two camelbaks around in my pack or dealing with the taste and hassle of iodine. Oh, and I still haven't touched that spare filter cartridge.

I purchased this a few months after it came out and decided to give it some time before I post a review. I've taken this on a few weekend trips and a handful of longer trips as well. Like every other review this thing was amazing at first and then slowed down after the first few trips. I backflushed multiple times after each trip, but it didn't get better. After overhearing a conversation at an outdoor shop in Austin I heard that MSR had a manufacturer defect with the first few batches that went out. I called and sure enough mine was one of the ones recalled so a new filter is in the mail.

Cascade Designs (maker of MSR products) is a great company with great customer service. I'm eager to try the new filter.

I gave this 3 stars b/c it is in incredible filter, but it could use a little more R&D. I have no plans to take it back since my backpacking trips are usually small 1-3 person groups and this is the perfect size for me.

Do not buy this pump. Three of us used it on a seven day trip. Each of us experienced the same hard to pump problem that other experienced and frustrated hiking brothers have shared. Although we pumped from clear clean sourced and followed the instructions for backflushing to the letter this pump FAILED with a capital F. It didn't work and we all ended up using another brand that one of our fellow hikers brought. MSR owes many of us trusted customers an explanation and refund.

I've been an Outdoor Educator/Guide for several years, and I recently brought a group of 12 to the High Sierras and used this pump by recommendation.
We were pumping mostly from sources that were SO CLEAN, it was tempting not to just fill up my Nalgene and be done with it--- especially after struggling with this pump.
At first it blew my mind how quickly the pump worked for moving mass quantities of water. A+ there.
Then, although we back-flushed frequently, the pump became painfully slow and difficult to use. By DAY 3 into our 15 day trip it was completely worthless! At that point, my fellow guides and I worked for about 2 hours!!! on this thing trying to salvage it. NOPE. Luckily, I believe that moving parts have a propensity for failure in the backcountry haha, and always back up my water sanitation system with time-tested Iodine. Thank god, because our trip would've been over.

BOTTOM LINE:
I think that for a SINGLE person pump, for SHORTER trips- where mass amounts (40-50 litres per day) of water are NOT expected: this is a fantastic pump! It's fast, light, & packs small. Home maintenance/cleaning may be extensive, but outside you'll notice a big difference from other pumps. (B+)

HOWEVER, For any realistic expedition (ie, lots of water needed and frequent use), this Pump needs to go back to the design table stat! because it was really and truly terrible. Even back-flushing every 8-10 litres (as per instructions), it couldn't handle the quantities we were dealing with. Epic FAILURE.

This was my first filter - boyfriend's 3rd, and he was far more impressed than I was. Using creeks and streams in the Cascades, we had no problems filling this up. Didn't need to do the backflush at all, but after 9L figured we would. If you follow the directions it's a snap. It's not an all-purpose filter, but works for us.

I bought this water filter to take to the high peaks on a 5 day backpacking trip. I went with two other guys and they were going to use tablets to purify their water. After seeing and tasting the water that I was pumping, I ended up pumping water for all three of us every morning and evening. The streams were extremely clear so the threat of the filter getting a large silt build up was not there. I couldn't be happier, I backwashed once. The pumping is so light that I carried everyday in my daypack. The only negative is that it did get a little harder to pump on about day 4. I did backwash with no problems. Great pump, I recommend highly!

Backflush is not that that difficult, but I recommend that you try it at home first just to figure out so you don't have to bring the instructions with you.
The only issue I had, which would probably be the same for all pumps, is keeping the inlet submerged. I ended using a spare water bottle, stuffing the inlet screen and tube into that, at using a rock to weigh it down. That worked fine.

I've used water filters in the Sierras since the late 1980s and was hoping that this highly rated unit would make the act of pumping less of a chore. When new, the thing really flows, but it only takes a few days and the filter will clog, even though I was using it in rather pristine clear water with prefilter. After 18 days in the mountains and only maybe 50% of the water we needed the flow was down to a trickle even with a lot of pressure applied on the pump. The worst part - the alleged back-flush option is a virtyual no-go. I sure could not figure out how to do it on and off the trail, and I am somewhat of an engineer. The thing simply doesn't budge when put together in backflush orientation. This year I plan on doing what most ultralight hikers do: bring a small bottle of bleach for water that may be suspect. Lighter, failproof, and considerably less aggravating than a pump that starts out fast but turns into a clogged pain after just days of use.

Well this filter may have its place but we tested
in 2008 at glacier . We talked to the MSR rep.
at the California outdoor show and he went through
the steps of backwashing the unit. Well we could not get the filter to backwasher at all, and after 3 days it was clogged.

It may be light but I'am not interested in taking the unit apart to switch the valves for back washing.

After returning from Glacier I called the rep. and he said they had some bad filter cartridges .

I'am going to continue to carry my 15 oz. First need water filter that has never failed yet.

I've been backpacking and climbing for over 20 years (I hate saying that...) and this is the best thing I've ever used to filter water. I'd been using it off and on on shorter trips in the Cascades and was blown away - but that's easy for most filters to accomplish. So, the proof was to be found on an 8-day trip in the High Sierras and I even bought a spare filter cartridge just in case. My research had turned up some folks griping about clogging etc. but I can only imagine that they were doing something wrong or filtering REALLY silty water. True - it does slow down if you are filtering really silty water. I noticed the difference between a glacial-fed lake and some others that were lower - but we backflushed as recommended (every eight liters, or about once every other day for two people) and had no problem whatsoever.

And for those worrying that backflushing that much is too much - think again. You'll never even consider going back to another filter after realizing how much easier the Hyperflow is. We got used to backflushing right as we finished filtering and it only added about 1-2 minutes - Far less than the time saved by the Hyperflow's speed and the overall ease of pumping more than makes up for any inconvenience you thought you might have felt. We even started to routinely do the filter test at the same time because it was so easy to do in the process.

I will say that I wouldn't use it in direct glacial meltwater and I have no idea how it would do in the Canyonlands or other places with really murky water, but I'm guessing it might not be the best choice there. However, if you want to get a superlight, and really small filter for taking on alpine trips or anywhere the water is pretty clear, I can't imagine a better set-up. I even take it on day hikes and car-to-car alpine climbs now and pump as I go. It beats lugging two camelbaks around in my pack or dealing with the taste and hassle of iodine.

Oh, and I still haven't touched that spare filter cartridge.

I have only used this one time, but so far its worked flawlessly. Small and lightweight, pumps wicked fast.