Water filter question

Is there a time when a water filter will not work? I’ve read that rangers suggest that water is not suitable for filtering retention ponds because the ponds were lined with non-porous sheeting like tar paper and just collect rain water for animals. I was just wondering, what are some of your takes on this. I’m not sure it matters, but I own the Katadyn Hiker Water Filter.

In brief, filters won't remove viruses (with a few exceptions), chemical contamination or many taste and odor issues. Really foul water might take both chemical and filtration treatment to be made drinkable--I prefer to push on to a better source.

Cheers,

I will repeat that filters won't remove most chemical contaminants. They also cannot cope with heavy metals from mine tailings that sometimes pollute streams near old mine sites.

There's one other condition under which a filter might not make water safe: if there are nasties smaller than your pore size, they'll pass right through. This is usually a localized problem, though. The only place I've encountered it is at Isle Royale, where there's a cyst that passes through filters with a pore size larger than .2 microns.

I'd only filter water from a retention pond as a last resort. I've never had to drink water from anything but a small stream, creek, or wilderness river.

Another time filters won't work is when it's below 32F. They'll freeze, develop small cracks you can't see, and that will allow the bad stuff to pass through.

Glenn, what did you use to treat/filter your water while at Isle Royal then? I am planning a trip there next summer. Any other information you might think pertinent to Isle Royal that you would like to share would also be most welcome.

-chris

It's been several years since that first trip. I called, and spoke to the ranger who was in charge (sort of) of the water quality issues. Based on his unofficial recommendation, I took the MSR Miniworks, because it was within the recommendations and because it could be cleaned in the field. (There's no bailing out and going back to the car for a spare element at Isle Royale.) The other filters he recommended were the MSR Waterworks (?), which is no longer made, and the two Katadyn ceramic-element filters: Pocket and Mini. I think the Sawyer filter I use now meets their recommendation for pore size. It's backflushable, and the extreme light weight would allow you to carry a backup without too much trouble.

Don't be afraid to call the rangers on the islands with questions. They're nice, and very helpful. Also visit the national park website and download a copy of the island "newspaper," which has a lot of good info.

The filter will work at any temperature. You cannot leave it out in the cold long enough to freeze, is all. If you are hiking in freezing temps chances are good you won't be filtering anyway - you'll be melting snow. If it is just subfreezing at night put the filter in the footbox of the sleeping bag.