SIFTING THROUGH THE FILTER JARGON

Which model works best?

First and foremost, have your water tested and determine what specifically needs to be filtered. Despite advertising claims, no filter can remove all water contaminants - and some remove too many beneficial minerals. No nonelectric filter can remove live bacteria. These must be eliminated by boiling or in a separate, prefiltration chlorine-treatment stage.

Some filters contain a single (ceramic or carbon/ion-exchange) element; others offer multistage filtration combining two to five of the following filtering/purification systems:

Mechanical particulate filter elements of fine-grained, porous ceramic that strain out dirt, sediment (turbidity) and other particles, including asbestos, parasitic flukes and their egg cysts, and some large bacteria. The government pure-water filtering standard is .05u (half a micron), but some filters will eliminate particles as small as .01u - small, but larger than most bacteria. Many portable hiker's ceramic filters can be renewed by simply scraping off the outer surface on the rough leg of your jeans.

Activated carbon filters contain beads of bone charcoal (elemental carbon) that are superheated/dried to become ionized, so they naturally attract metallic elements and many stray organic molecules. They capture lead, mercury, chlorine, sulfur, VOCs (volatile organic chemicals such as the pesticide Lindane) and biological sources of bad taste and odor. Carbon filters can be partly restored by washing and superdrying.