Is it safe to filter water from a still pool?
I have one of the new MSR MiniWorks EX water filters, my first, and it works great. One of my buddies tells me to filter water from a still pool, but another says to filter from fast-moving water: Do you think it matters much? Personally, I just try and go for the clearest water I can find. Mike Eldorado, Illinois
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Yeah, I sure do think it matters, as it’s a matter of garbage in, garbage out. As a general rule, still water is apt to contain more little bugs and other crud because the nasties have a better chance to multiply or pick up bad things when not getting knocked around in a current. Moving water filters itself better, removing either particles than can clog a filter or microorganisms.
In any event, you’re on the right track: Find the clearest-looking water and start with that. My preference is to find a little pool in a moving stream. That way the tube float isn’t bobbing around too much, but the water still comes from a moving source. Keep in mind that dirt and grit can cause real problems with a filter, so you want to avoid filtering water that looks dirty if at all possible. The PUR filter folks suggest a few good tricks to help with this (www.purwaterfilter.com). One is to draw some water into a bucket or water bottle and let it settle for several minutes. Another, strain it first through a paper coffee filter (which can be re-used if you’re careful). Either of those steps will go a long way toward prolonging the life of the filter.