Geoscience Reference
In-Depth Information
For reduction of bacteria, tests indicate that the MSR WaterWorks II and the Katadyn
Combi Filter perform the best out of the longer-lasting portable filters. Test users liked the
Katadyn Pocket Filter and the MSR MiniWorks best for simplicity and ease of use and service.
After testing numerous models, the U.S. Marine Corps selected the MSR MiniWorks for use by
its Amphibious Raids and Reconnaissance Division. Katadyn was the third-world traveler's
standard for many years, but MSR is giving Katadyn a lot of competition.
The MSR units and the Katadyn Combi Filter have the benefit of activated carbon, which
will help remove chemicals, bad tastes, and unpleasant odors until the carbon is used up (the
ceramic filter element should continue to provide bacterial and protozoa protection long after
the carbon is spent).
Even though these units remove about 99 percent of most viruses, they are not rated as pur-
ifiers, so if viruses are a significant concern (for example, if your only source for water is the
local duck pond or a river in a highly populated area), you should chemically treat your water
before running it through one of these filters or zap it with a SteriPEN after filtering.
Heavy Usage, Not So Portable
If I wanted to provide purified water for several people over a significant period of time, I
would buy one of the recommended gravity-fed units. The per-gallon cost of these units is a
fraction of the cost per gallon of using a small portable pump purifier, plus you do not have to
sit there and pump away for long periods of time to provide a large quantity of purified water.
Gravity-fed units either have a top reservoir that holds the source water while it slowly per-
colates through the filter media into the bottom reservoir of purified water, or they are siphon-
type units designed to siphon water from one container to another. Gravity-fed units require no
pumping but cannot produce water nearly as fast as the recommended high-volume, pump-type
unit.
Where viruses are a concern, you should chemically treat your water before running it
through one of these filters, or zap it with a SteriPEN after filtering.
Recommended gravity-fed units are the various Berkey models, the Katadyn Drip Filter,
and the AquaRain model 200 and model 400 filters. The Big Berkey filter, with two “Black
Berkey” purification elements ($279) has a rated capacity of 4 gallons per hour, a life of up to
6,000 gallons, and the carbon block filter elements may be cleaned with a Scotch Brite pad to
restore the flow rate.
The Katadyn TRK Gravidyn Drip Filter ($250) has a rated capacity of up to 13 gallons per
day and a life of about 2,300 gallons before the carbon core is saturated, but will continue to re-