Pure Backcountry Water

There are dozens of ways to purify your water in the wilderness. Here’s how the most common methods compare.

METHOD	HOW IT WORKS	REMOVES/KILLS	PROS	CONS
Boiling	Boil water for at least four minutes.	bacteria, protozoa, viruses	No additional equipment required if you already have the fuel, stove and pot in your pack. Doesn't alter taste of water.	Water remains discolored. Particles in water unless strained. Can take awhile at high elevation. Amount of treatable water is limited to size of pot. Uses fuel. Has to cool before pouring or drinking, unless you want a hot drink.
Filter	Water pumps from source through container.	bacteria, protozoa (It must have an iodine filter to remove viruses.)	Removes most particles. Doesn't alter taste of water.	Filter must be changed. Chance that pump can break. Intake valve and waterbottle cap should to be kept apart. Difficult to drain after use. Won't remove viruses. Pumping can be tedious.
(pore size 0.4 microns or less)	Water pumps from source through container.		Removes most particles. Doesn't alter taste of water.
Potable Aqua	Iodine tablets: Add two tablets to a quart of water. Wait 30 minutes.	bacteria, most protozoa, viruses	Lightweight. Space-saving bottle of pills. Easy. Cheap ($6.50 for 50 tablets).	Won't kill cryptosporidium. Limited shelf-life (four years unopened; less than a year if opened). Water tastes bad and is discolored, though you can but taste neutralizer tablets. Some people are allergic to iodine. Particles in water unless strained. Not recommended for pregnant women or people with immune difficiencies.
Aqua Mira	Chorine dioxide: Mix drops. Add to water. Wait 20 minutes.	bacteria, protozoa, viruses	Lightweight. Space-saving small plastic bottles. Easy. Cheap ($14.00 treats up to 30 gallons) No chemical taste.	Particles remain in water unless strained. Takes longer if water is cold or very dirty.
Steripen	Ultraviolet zapper: Place end of "pen" in water and stir. Works in under two minutes.	bacteria, protozoa, viruses	Lightweight. Space-saving. Easy. No maintenance. Very quick.	Water must be clear. Uses lithium CR123A batteries (alkaline batteries work, but only last for a few treatments). Batteries can fail, especially in cold weather. Expensive (up to $100 depending on model).