I saw a review on Backpacking Light's website that indicates that it's possible (and maybe not all that hard) to create an "irreversible airlock" when trying to backflush the filter. By itself, that would be a minor annoyance. However, the poster said that he was told by his outfitter that the airlock ruins the element, requiring replacement (and that MSR is replacing elements damaged this way free of charge.)

Offhand, that seems like a pretty obvious flaw that preliminary testing would have quickly turned up. Jason: care to bust this myth, or confirm it with additional information? (I was almost persuaded to go ahead and replace my problem-free Miniworks, but now I'll wait until I see what's going on.)

Here's the link to the review:

http://www.backpackinglight.com/cgi-bin/...thread_id=13957

In all fairness, the other review on the website said the Hyperflow was a great filter.

Interesting. I discussed this with a guy on Whiteblaze. We have both had the problem where the red check valve "puckers up" during the back flush not allowing anything through it. The only way to resolve the issue is to take the filter back apart, pull the valve off, start over and hope it works. Is this the airlock problem being referred to in the BPL thread? Is my filter now "broken" and in need of being replaced?

I'll be interested to hear input from others and Jason on this.

Since nobody responded yet, I will give my opinion on this based purely on conjecture. As indicated I do own a Hyperflow, and I have had the "Airlock" problem occur. Other than that I have enjoyed using the filter as it is light, small and has a decent output rate. From visual inspection of the filter after a trip where it airlocked several times during attempted back flushing, I don't see any physical damage to the filter element. So I would say that it is a myth. Unfortunately there is no way to prove it though. I could run the test given in the instructions to see if there is an issue, but even that does not appear to be definitive from accounts of others that have run the test on "good" filter elements with uncertain results. So that's my 2 cents for what it's worth.

I have contacted the person in charge of water treatment at Cascade Designs via email and will let you know what I find out in the next few days.

Berserker and Jason:

Thanks. I'm definitely interested in it (as in, I put it on my birthday and Christmas lists.) It gets that last half pound out of my pack.

I appreciate hearing your experience, Berserker; it's reassuring. I'm thinking that this will become my weekend filter, since I'll be hiking solo and won't need more than 6 or 8 quarts of water for two days; I also carry a nylon bowl so I can dip water and let the sediment settle before pumping. I can do the backflushing at home, and deal with any airlock issues when they aren't critical to a trip. (My Miniworks will probably remain my filter for trips longer than a weekend, since cleaning is a definite non-problem.)

Jason, thanks for taking it to an authoritative source. I wanted to get some additional reliable information before it became a case of "This filter is flawed; it says so on the Internet."

Glenn

I recently bought the Hyperflow. I have only used it once, but I am impressed with it so far. My original intention was to buy the Miniworks, but after seeing how heavy it was I changed my mind. The store clerks were both using the Sweetwater model which is lighter than the Miniworks, They recommended I give the Hyperflow a try since it is even lighter and faster than the other two. I cannot comment on the back flushing problem as I haven’t done that yet. It seems to be a very good unit. I met a man on the trail who had one too. Like me he hadn’t used his a lot but he was finding it to work real slick.

Howie

Glenn, I thought I would give you a little more info on the Hyperflow. I intended on writing up a detailed report on it after I use it again, but I probably won’t get out until August. So, based on one 7 day trip where I used it about 2/3 of the trip I’ll give you my observations.

First off, I use Platypus containers and a soda bottle. This is an important detail because the Hyperflow output fitting “press fits” into the opening of these containers. So basically I can push the filter output fitting into the container opening, and the container just “hangs” there while I am pumping. Surprisingly, the fit is quite snug, which is really nice because I haven’t yet had a container fall off while filling it.

On to my general observations. As indicated in my earlier post, this filter is light (8.64 oz on my scale for everything except the wide mouthed bottle adaptor), small and outputs a lot of water on each pump. I have found that the pumping action on it takes a little practice, and does require some force. If one were to pump 4 – 6 liters at one time like I typically do, this thing will wear you out. Whipping it out just to do a liter during a break is pretty nice though. The other thing about the pumping action that is a little annoying is that the part of the filter where the output fitting goes into the container is also within close proximity to one of the hand holds for pumping. This makes it pretty hard not to touch the container opening with ones hands while pumping. Not a big deal, but I wouldn’t want to do any filtering with really dirty hands. I have also noticed that the pre-filter is a little finicky, and it is sometimes challenging to get it to sit in the correct orientation in the water.

The back flush has gotten a lot of bad press. When I initially bought the filter I thought that doing a back flush every 8 liters would be the deal breaker just because of the extra work. It really hasn’t been that bad, and frankly being able to field maintain the filter is a nice option since other filters (like my Katadyn Hiker) are toast once they get backed up. The back flush, when it works properly, only takes a couple of minutes. I created a setup where I attached some cords to one of my 1 liter platy Hosers. I just hang the Hoser upside down on a branch, pull the mouthpiece off of the drinking tube, and push that right onto the smaller nipple fitting on the output of the Hyperflow. Then I just pump it 10 times and I’m done.

My main complaint at this point in time is that I have had the airlock problem while trying to back flush. What is weird though is that during the trip I was able to get the back flush to work after a few separate attempts, and then it worked every time after that. Basically what was happening with my filter is that the smaller red check valve (there are 2 that have to be reversed to do the back flush) was somehow getting a “suction” created on it. Once this happened the only way to break the suction was to open up the filter and pull the valve out thus removing the suction. I don’t know if it was just a “break in period” thing or what, but the smaller check valve finally loosened up a little where it would let the water through on the back flush without the suction being created.

So what are my thoughts...I think like the Hyperflow. I still need to get out again with it on a trip where the back flush actually works properly, and then I may really like it.

According to Sarah, the watertreatment product manager at Cascade Designs, this was her response to my email:

No, the filter cartridge definitely does not need to be replaced if it gets air-locked, the check valves simply needs to be reversed, filter water in the forward flow direction to purge the air and then re-follow the directions for backflushing the unit.

She also mentioned that there was some confusion by the costumer service personnel at CD when helping folks over the phone. In some cases, as a last resort, Cascade Designs found it best to send them a new filter element, not knowing fully what the problem was. They sent out a new filter element only on that rare occasion, but not based on the airlock issue. As with any of their products, CD wants to make sure the customer is totally satisfied with their purchase. Simply stated, the filter element cannot be damaged due to it being airlocked.

It should also be said that it takes a significant amount of force to actually hurt the Hollow Fiber membrane. I've accidently dropped mine on several occasions without any issues (I don't recommend anyone do this however). I haven't yet frozen it, but I suspect that would take a fairly solid freeze to cause any damage. I HIGHLY recommend that the user avoids as much as possible dropping or freezing the filter membrane, but I wouldn't think that anyone should lose sleep over it. Cascade Designs simply wants to make sure the user takes care of their new pump and to not throw it around. This is to insure that the pump will filter water when needed without worry.

The other thing the backpackinglight.com reviewer mentioned was that you can never be certain if the element is damaged even if tested. In reality, it is fairly easy to see if it is damaged based on the bubble test. Simply stated if you don't see any bubbles in the water, the filter is good. However, if you see a series of bubbles when pumped during the test, the filter is damaged and needs to be replaced. It is a very clear indicator of its condition. I would recommend that if the unit is dropped and there is a worry it has been damaged that you immediately perform this test. You will clearly see whether or not, in a few minutes, if damage has occured. It is a simple test.

It is true that you need filtered water to perform the backflush (as mentioned by the reviewer), but this only makes sense. All this means is that you don't contaminate the output portion of the filter. If it were me, I would go to great lengths to eliminate any contamination to this area of the filter. In fact, this is one of the design features that sets it apart from other filters that have two hoses. With two hoses, the user can inadvertently drag them in the dirt or lake/stream being filtered from, thus contaminating the output. However the HyperFlow (and MiniWorks EX for that matter) requires that the bottle be attached directly to the filter. If a hydration system is being used, the hose can be attached directly to the output. And when you are finished using the filter, there is a cap that goes over the output. Avoiding cross-contamination is one of the key elements to insuring the user doesn't become sick.

Thanks, Jason - I thought that the BPL review might be a bit extreme, coming from the combination of a new product, and a salesperson trying to pass along to his or her customer all the information (and hearsay) he or she had at that point, trying in good faith to help the customer make an informed decision. Now we have not only a quantity of information, but a little better quality, too.

And Berserker - thanks again for the thorough, factual, straightforward info on the filter. It's now definitely on the gift list - if I can contain myself that long!

I just took mine on its inaugural hike as well. I loved the fact that I had a full 2L bladder in less than a minute, including unpacking and repacking the unit. I'm a pretty impatient guy (until I'm at camp with a book and an ounce or two of single malt..) so this was a big deal for me!