How well a filter works is based on its “absolute” pore size.
Protozoa – 2 to 200 microns
Bacteria - 0.1 to 15 microns
Viruses - 0.01 to 0.03 microns
Human Hair (Diameter) 80-100 microns
· Filters with a pore size of less than 2 microns will eliminate Protozoa.
· Filters with a pore size of 0.1 – 1 microns will eliminate most harmful Bacteria.
· Filters cannot filter out Viruses because of the inability to achieve a pore size small enough.
· Bleach and Iodine used after filtration or boiling the water will eliminate the viruses.
· Charcoal Filters need replacing more frequently.
· Ceramic Filters (replaceable) can develop hairline fractures .
· Make sure the filter is field serviceable & easy to clean.
· Fast flow rate (at least a liter/quart per minute).
Backpacking Water Filter Buying Guide