Gear Review: In-Bottle Water Filters

10:36 a.m. on November 16, 2009 (EST)
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130 forum posts

This thread is for comments on the article "Gear Review: In-Bottle Water Filters"

While each type of water filter system has its pluses and minuses, bottle-based filters offer extreme portability and simplicity. See how the ones we tested fared during backcountry use.

Full article at

6:17 p.m. on November 18, 2009 (EST)
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28 forum posts

I beg to differ with Mr. Werner's statement that "all these filters remove bacteria and protozoa-----"

The two largest microfilter companies MSR & Katadyn (I am the Northern Rockies representative for Katadyn) both use much smaller pore size filters than is found in most of the bottle models listed.

It is generally accepted that a pore size 0.3 micron or smaller is needed to remove all disease causing bacteria from water in North America. The standard test bacteria, e coli, is quite large on a microscopic scale and is usually stopped by a 2.0 micron filter. However several bacteria common below livestock, Campylobacter, Salmonella, Shigella, and others: are small enough to pass through 2.0 micron filters.

These bacteria are definitely a cause for concern when drinking water below livestock.

Campylobacter has also been found in water at 7,700 Ft. in the Tetons and is apparently spread by waterfowl feces in some cases. In a 1980 study 25% of hikers getting ill in the Tetons were found to be infected with Campylobacter.

So I think filter size is important.

Outback is 2.0 micron. They correctly assert their product is designed to remove protozoa.

Aquamira was a little difficult to find pore-size on. I could not find it on their website, but uses what looks like factory data and says 3.0 micron.

Katadyn is 0.3 micron.

ECh2O-----their website says removes giardia, cryptosporidium, and other cysts. Since it does not say bacteria-----I will guess their pore size at 2.0 microns.

To sum up: pore SIZE MATTERS-------at least in water filters.

8:51 p.m. on November 18, 2009 (EST)
130 reviewer rep
130 forum posts

Pore size is one of many factors that affect filter effectiveness, but it's not the sole determining factor, despite what manufacturers would have you believe. Filter porosity, test water pressure, pore shape, manufacturing consistency, filter composition and tortuosity, are also equally important and effect the removal rates reported by so many manufacturers.

Claims about pore size are so misleading to consumers that REI won't list them in their gear guides and just list the organisms a filter removes. I agree with them for the reasons listed above.

As an aside, Dennis Brown at Aquamira has written an excellent paper about the confusing terminology put out by water filter manufacturers that's worth a read if you are interested in debugging water filter manufacturer marketing claims: Here's the link:

I do agree with you that small bacteria are a concern in certain areas of the US, but I don't agree that pore size is the fix-all that you claim. Water filters have their limits and when in doubt about water quality, people should use a different method, such as a purifier, or a combination of methods such as a filter and chlorine dioxide tablets or ultraviolet light.

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