While recent research has concluded that backcountry water sources (especially those at higher elevations) are cleaner than once thought, it is impossible to tell which water sources may be contaminated. Rather than risk serious intestinal discomfort there are many water treatment options available, but which is best? Choosing a water treatment system for backpacking can be a confusing and time consuming process. Below we review the options available and discuss the various pros and cons of each to help you decide.
Pump Filtration:
There are many different pump filtration systems out there. Most work by placing one end in the water you wish to filter and the other in a storage container and then manually pumping the water through the filter. Pump filters utilize a variety of filtration media including ceramic, fiberglass, silica, etc. Membrane filters use thin sheets of material with fine pores; they are relatively easy to clean but clog easily. Depth filters use thick layers of porous media; they can be harder to clean and if the media is cracked the filter is ineffective. Micron size (a measurement of the pore size in the filter media) varies by filter so make sure to select a filter with a micron size that is effective at straining most protozoa and bacteria.
Pros:
- effective against protozoa and bacteria
- strains out particulates
- relatively fast
Cons:
- not effective against viruses
- moving parts require maintenance
- can become clogged
- pumping too fast may reduce effectiveness of filters
- weight (varies by system)
Gravity Filters:
Gravity filters work by letting gravity push the water through the filter for you. Generally you fill a large bag with water and hang it from an obliging tree or rock. Some gravity filters come with storage (water filters into another compartment) while some do not.
Pros:
- lightweight
- easy to use
- few moving parts
- little maintenance required
- effective against protozoa, bacteria, & cryptosporidium
- relatively fast
- good for treating water for large groups
- strains out particulates
Cons:
- cost
- does not work against viruses
- puncturing the bag or letting the filter freeze can ruin the system
Filtration Straws:
Straw type filtration systems work by filtering water as you sip. They are available with or without storage bottles.
Pros:
- lightweight
- inexpensive
- easy to use
- effective against protozoa and bacteria
- little maintenance required
- strains out particulates
Cons:
- does not work against viruses
- for immediate consumption only
- must be replaced if it becomes clogged
UV purifiers: 
UV systems purify water by exposing microorganisms to UV light for around 90 seconds. The light inactivates microorganisms by disrupting their DNA.
Pros:
- lightweight
- effective against protozoa, bacteria, viruses & cryptosporidium
- does not change the taste of the water
- good for small bottles of water
- relatively fast
Cons:
- requires batteries
- bulb has a limited life
- effectiveness is lowered by cloudy water
- does not strain out particulates
Chemical Treatment:
Iodine and Chlorine dioxide provide a lightweight option that is useful for treating large amounts of water. Typically tablets are dissolved in water; treatment usually takes between fifteen and thirty minutes depending on the chemicals used. When using chemical treatment it is important to follow the directions on the bottle.
Pros:
- lightweight & compact
- inexpensive
- iodine is effective against protozoa, bacteria & viruses
- chlorine dioxide is effective against protozoa, bacteria, viruses & moderately effective against cryptosporidium
- useful for treating large amounts of water at one time
- great as a backup water treatment option
Cons:
- water may have a slight taste after treatment
- tablets/chemicals may become ineffective after their expiration dates
- cold water (less than ~60F (16C) decreases the effectiveness of the treatment and requires longer treatment time
- some people are allergic to iodine or shouldn’t use it due to medical conditions
- does not strain out particulates
Boiling:
Bringing your water temperature up to 212F (100C) is one of the simplest water treatment options.
Pros:
- very effective at killing all microorganisms
Cons:
- slow
- requires fuel & a fire
- not suitable for large amounts of water
- higher altitudes requires additional boiling time as water boils at a lower temperature
- does not strain out particulates
