Well, by "fail" I basically meant mechanically, visibly so- like part of it coming out or not fitting together. Obviously the only way to really know is if you get sick or die, but that can also be said of every other portable method of cleaning/purifying water. Even boiled Dioxin or Benzine would probably still kill you, wouldn't it?
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman