In A Nutshell
Portable water filters have improved in recent years — manufacturers are now producing units that filter contaminants the size of nanometers (a billionth of a meter).
The best portable water filters available today are:
- The Sawyer Products Complete 4-Liter Filtration System. Filters down to 0.1 microns. This includes almost all pathogens, except certain viruses. It costs about $180.
- The Katadyn Pocket Water Microfilter. Filters down to 0.2 microns. It costs about $340.
Another reliable method of killing all pathogens in water is using chlorine dioxide tablets, such as Katadyn Micropur Purification Tablets.
Portable filters are designed primarily to remove pathogens from outdoor water. Some units also include carbon filters to reduce VOCs and toxic metals in the water.
These are the three type of pathogens you want to remove from wilderness water:
Protozoan Cysts (Cryptosporidium parvum, Giardia lamblia)
Size: 1 – 20 microns
Type of filtration needed to remove: Micro-filtration, ozonation or reverse osmosis, UV (ultraviolet light)
Bacteria (E. coli, Salmonella, Campylobacter jejuni, Yersinia entercolitica, Leptospira interrogans, etc.)
Size: 0.1 – 10 microns
Type of filtration needed to remove: Micro-filtration needed, ozonation or reverse osmosis, UV (ultraviolet light)
Viruses (hepatitis A, rotavirus, enterovirus, norovirus, Norwalk virus)
Size: 0.025 – 0.1 microns (25 nanometers to 100 nanometers)
Type of filtration needed to remove: Ultra-filtration needed – ozonation or reverse osmosis, UV (ultraviolet light)
Notes On Pathogens
- Pesticides, herbicides and other toxins and pollutants associated with agriculture and urban development do not normally impact water sources found deep in wilderness areas
- Viruses are rarely encountered in North American wilderness waters
- Bacteria (including beneficial bacteria) is naturally present in surface water
- Protozoan cysts and viruses are found in water contaminated by animal or human waste (principally feces)
The Best Portable Water Filter: Katadyn Pocket Water Microfilter
The Katadyn is a dependable filter which has been used by back country hikers for many years. The filtration member is rated at 0.2 microns. The silver-impregnated ceramic element is effective against bacteria and protozoa, and it will filter 50,000 liters (13,000 gallons) before a replacement is needed.
The Katadyn Pocket Water Microfilter is available from Amazon for about $340.
Another Alternative: Sawyer Products Complete 4-Liter Filtration System
The Sawyer Filtration System is an excellent kit, that filters down to 0.02 microns, using a hollow fiber membrane. That’s almost on par with the Lifesaver, with it’s 0.015 micron filtration. Thus, the Sawyer can filter out most pathogen, including viruses.
What’s great about this system is that it almost never needs a replacement filter. The manufacturer has a guarantee that it will filter one million gallons before replacement. However, long-time users report the water reservoir bags need replacing after a couple of years.
The Sawyer System is gravity-fed, and allows you to purify 4 liters of water in about 10 minutes.
The Sawyer Products Complete 4-Liter Filtration System is available from Amazon for about $180.
Chlorine Dioxide Tablets
Chlorine dioxide tablets are a good choice for water purification. They will destroy all pathogen in water. Also, they leave no taste in the water (unlike iodine tablets). Like all water treatment tablets, these take 15 minutes to destroy viruses and bacteria, 30 minutes to destroy Giardia, and 4 hours to destroy Cryptosporidium.
I recommend the Katadyn Micropur MP1 Purification Tablets. This is only tablets registered with the EPA.
You can boil water for one minute to destroy all pathogens. It is a foolproof treatment method. Only one minute of boiling is required. The most heat-resistant pathogen out there is the virus hepatitis A. Even hepatitis is believed to die in less than one minute in water heated to 98°C/208°F. It is because of hepatitis A (or maybe just tradition) that some health organizations and wilderness rangers persist in recommending at least 1 minute of boiling time to purify water, and 3 minutes at higher elevations.