"Not sure what went wrong" - Review of MSR HyperFlow Microfilter

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.
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