How to Choose a Backcountry Water Filter

Steven using Katadyn backcountry water filter on Pennsylvania river

Proper hydration is essential for an enjoyable trip. Carrying water is manageable for short trips but as any wildland firefighter will tell you, water is not a lightweight liquid (1 gallon = 8 pounds). If you plan to utilize water sources along your route, you’ll need know how to choose a backcountry water filter.

There are several ways to remove or neutralize the nasty protozoan cysts, bacteria and viruses that occur in these water sources. Like much of the other gear you choose, water treatment devices are a very personal choice, with pros and cons to each method.

filtration versus Purification

When considering how to choose a backcountry water filter, an important consideration the difference between filtration and purification. Water filters remove the two main threats to hikers in the U.S. and Canada: waterborne protozoa (tiny little animals such as Cryptosporidium and Giardia) and bacteria (such as E. coli and Salmonella). They do not remove viruses (such as Norovirus and Hepatitis a.)

Water purifiers, on the other hand, neutralize protozoa, bacteria and viruses. Some also offer additional protection against agricultural or industrial contaminants such as fertilizers and metals.

A microfilter (one that removes contaminants down to 0.2 microns) should ride in your backpack when you’re in the backcountry of the U.S. and Canada. Similarly, a water purifier is an indispensable item in your travel pack when touring developing countries with questionable water filtration systems or different sanitation practices.

Water Filters

Pump-based Filters

Pump filters consist of an encased filter membrane with a plunger or handle and lightweight tubing. Use the plunger or handle to pull water from the source through the tubing, then into the filter and out another tube into your bottle or other container.

Steven holding Katadyn pump filter along Pennsylvania river

Great things about pumps filters:

  • Pump straight from the source, with no need to fill a reservoir first
  • No need for a deep source of water; just find enough to cover your intake hose
  • Filter cartridges are replaceable

Things you’ll want to keep in mind:

  • Intake and output hoses need to be stored separately to avoid cross-contamination
  • Some field maintenance, such as backflushing, may be necessary
  • Pumps can be heavier and bulkier than some other methods

Pump-free Filters

Gravity filters

Hang a container of water, then let the water drain down through an in-line filter and into another container for use. Some scoop-type bags need a relatively deep pool but these filters are small and lightweight and usually less expensive than pump units. Gravity filters require waiting for the water to drain through the filter but, during that time, gravity does all the work — no pumping necessary. You can attend to other camp tasks as your water bag fills.

Steven using a Katadyn gravity filter along a Pennsylvania river

Squeezable filters

In these small, lightweight filters, your manual squeezing action moves the untreated water through the filter. Although it requires labor similar to a pump filter, squeeze filters clean water faster than a gravity filters.

Steven using a Katadyn squeezable water filter

Straw filters

Some filters are built right into a lightweight drinking tube that you insert directly into the water source. This allows you to filter and drink simultaneously. Because you can only drink while you’re at the source, and there’s no method for storing clean water for later use, many hikers uses these in conjunction with another treatment method.

Water purifiers

Pump-based Purifiers

Pump purifiers work similar to pump filters, but either (a) use a more advanced membrane to trap viruses or (b) work in conjunction with chemical tablets that neutralize viruses.

One of the most advanced pump purifiers on the market is the MSR Guardian. In cooperation with the US military, this purifier was developed to provide safe drinking water anywhere in the world.

Pump-free Purifiers

UV Purifiers

Rather than filtering water, UV purifiers neutralize protozoa, bacteria and viruses with ultraviolet light. These small, ligthweight devices signal exactly when to stop and start; you merely stir the wand for about a minute and your job is done. UV pens do require batteries, so it’s wise to carry extras.

UV purifiers don’t clean dirty water, so you should remove leaves, dirt and other debris from your water. Pre-filtering dirty water does more than make your water more palatable: debris particles can decrease the efficiency of UV purification and even block UV rays, leaving pathogens untreated.

Steven using Steripen UV water purifier

Chemical treatment

Iodine or chlorine-based pills and drops are an inexpensive, extremely lightweight method for treating water. Chemical treatments requires waiting and some dislike the slightly altered taste. Just add the recommended dosage to your water and wait (methods vary from 30 minutes to 4 hours depending on variables like the water temperature). Many backpackers use this as a safety net in case their filters or UV pens fail.

Also keep in mind that iodine isn’t effective against Cryptosporidium protozoa. It can also be a concern to pregnant women and people with thyroid conditions.


There’s always the old fashioned way. Just bring a pot of water to a rolling boil for one minute, or three minutes if you’re above 6,500 feet. You’ll need a little patience for the boiling and cooling to take place. Remember that you’ll need to pack extra fuel for the frequent boils. You’ll also be limited by the size of your pot. Despite the fuel and time requirements, boiling is a reliable and low-tech way to kill the biological contaminants in drinking water.

The Takeaway

Selection of water filters on mossy background: 2 pumps, squeeze filter, UV purifier, and gravity filter

You know that proper hydration is vital to a pleasant hiking experience. But the same water that keeps you quenched and strong can also bring your trip to a screeching halt if it’s not clean. The wilderness is no place to roll the dice on a stomach illness. Filtration is sufficient in most of North America, but seriously consider purification if you’re traveling abroad. Learn how how to choose a backcountry water filter so you can stay hyrdated and healthy on your travels.

stay hydrated on the trail!

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