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