For those new to backpacking, one area of backcountry travel that might seem daunting is water treatment. You probably have a ton of questions. Do I even need to filter water? How expensive are filters? How long do they last? Are there other treatment options? Perhaps you’re completely new and don’t know where to begin. Here, we’ll share everything you need to know about filtering water in the wilderness.
I’ll start with this: it’s a good idea to treat water in the backcountry. Sure, you’ll find plenty of dirtbag thru-hikers espousing the benefits of drinking unfiltered mountain water. But for every voice pushing the #nofilter lifestyle, you’ll find many, many more who will be happy to share their lovely experience battling giardia miles away from the nearest indoor plumbing. Given the downsides, why take the risk? Plus, treating water allows you to relax streamside and get off your feet.
Why should you treat water?

Picture this – It’s hot outside. Like, really hot. You’ve been sucking air out of your bladder for the last 30 minutes and are dying for some crisp and cool mountain water. A creek appears! It’s crystal clear, oh-so-cold, and bubbling pleasantly. Everything is good, right? Sure, except for that dead raccoon rotting in the water around a bend 100 yards upstream. The truth is, you generally can’t be sure what’s in the water, no matter how clear and clean it looks
There are three main ways to clean water in the backcountry:
Filtration
Water filters are filled with small tubes that have even tinier holes (as small as 0.1 microns wide). As water is forced through the filter, water molecules can pass through the holes, but many pathogens can’t. Filters are very effective for straining bacteria and parasites (including giardia and cryptosporidium – two common sources of backcountry bowel distress). However, they cannot filter viruses. To keep them in good use, you’ll have to backflush the system regularly.
Chemical treatment
Chemical treatment comes in several forms, including iodine drops and chlorine tablets. These chemicals kill many pathogens and are safe to drink when used according to directions. However, they do NOT get rid of particulate matter (like pieces of dirt or plants) and are only somewhat effective against parasites. They typically leave a mild taste in your water as well.
UV treatment
UV rays are highly effective at killing bacteria, viruses, AND pathogens. They usually come in the form of a pen that is inserted into dirty water and stirred around for a certain amount of time. Like chemical treatment options, UV pens do not remove any particulate matter from a water source.
Our recommendation: filter water
We’ve backpacked thousands of miles through all kinds of terrain and feel that filtration is the best method for treating backcountry water. Modern filters are small and light. They’re extremely portable and filter a liter in a few minutes. Squeeze filters like the Sawyer Squeeze are compact while gravity filters pack a bit more size, but don’t require squeezing to operate. Most squeeze options are able to screw right into a standard plastic water bottle.
Although filters don’t get rid of viruses (like hepatitis A or norovirus), those are highly unusual to find in a backcountry setting in the United States. My biggest issue with both chemical and UV treatment options are that they don’t filter out the mysterious flecks of earthy matter that are bound to get into your bottle. And while UV light is extremely effective, it can sometimes be difficult to tell if they’re fully operational. I’ve had battery issues with a pen before and was uncertain whether the UV had deployed correctly.
Along with a squeeze filter, we also bring a small supply of chemical tablets as well. If you have to filter from an extremely filthy source (see: photo of a cattle trough below), you can always double up and add some chemical protection in addition to the filtration.
Here’s how to backflush a filter
The one downside to using a squeeze filter is that you’ll have to perform a bit of trailside maintenance from time to time. After a while (sometimes, after a short time if you’re filtering filthy water), you’ll need to backflush your filter. This means forcefully shooting clean water in the opposite direction through your filter to clear out all the gunk.
Backflush your filter after every trip and whenever it gets annoyingly slow. For shorter trips, you can probably do this afterwards from the comfort of your home. For longer trips, you might have to perform this while on the trail.
A squeeze filter will come with a backflushing syringe that will fit right onto the nozzle. Fill your syringe with CLEAN water, and then forcefully shoot it through your filter. The debris will explode out the other end, which is quite satisfying to see. Keep backflushing until the water runs clear.


A final very important note on squeeze filters
Once water is pushed through a filter, a small amount will remain inside the filter. You should never let your filter be exposed to air below freezing. The water trapped inside will freeze and expand, cracking the tiny holes inside. Once this happens, the tiny holes will be slightly larger, which could enable the passage of harmful bacteria. You may not be able to tell that this has happened, as the flow rate won’t greatly increase. So – if you’re camping in cold weather, make sure to pack your filter into your sleeping bag at night!