Water Filter and Water Purifier Guide

There’s nothing like an ice-cold mouthful of water after a hot, hard hike in the backcountry. I often equate it to peeing under the Milky Way — basically an essential backpacking experience. That water rarely comes straight from the source, though. It’s been filtered or purified so that, hours after quenching my thirst with nature, I don’t feel the first tendrils of some waterborne pathogen.

Nobody wants giardia on a good day. You especially don’t want it (or anything else lurking in a stream or river) miles from civilization. So you pump, you squeeze, you mix in drops or tablets and shake vigorously, you let ultraviolet light destroy the viruses, and, when all else fails, you boil the hell out of that water before you drink it.


A few water filters and water purifiers waiting to clean water.

The unfortunate reality is that in much of the developed world you shouldn’t drink straight from the source. There are exceptions, but bodies of water in the U.S., even in the backcountry, should be filtered or purified prior to consumption.

This Outdoor Guide will explore why we treat water, the specific methods in which backpackers and travelers treat water, and what options are best for you. Scroll to a specific section with the Table of Contents below, or read the whole thing. (It’s for your own good, I promise.)

Why Treat Water in the Backcountry

Gone are the days when you could come around bend in a trail, discover the rushing sound of water, bend down, and drink your fill. That time is romanticized in backpacking culture — a past when water was good no matter what, and you could live off the land without the need of modern instruments.

Actually, the idea is so romanticized that some people still do it, regardless scientific studies and Center for Disease Control fact sheets, all of which confirm that there are pathogens in the water you’re drinking. Different studies have come out debating this; TheTrek sums the bulk of these up very well, citing a number of sources, all of which are steadfast in their advice: treat your water!

water-filter-and-water-purifier-dirty water

You definitely want to treat this water. Photo by Lee Canon via Flickr.

There are a few rare instances in high-alpine environments where it may not be necessary, but this won’t apply to most people. Even if you wanted to get to those pristine water sources you would have had to climb up there, and water filters or purifiers are standard recommended gear for extreme trips like that.

Livestock, wild animals, human traffic on trails, environmental decline, and a number of other reasons contribute to the degradation of water quality. So, what exactly are you avoiding?

What Are Pathogens In Backpacking Water Sources?

The word is pathogen scary, and you should be scared. Pathogens can mess you up, especially your digestive tract. Pathogens usually come from human and animal fecal waste. Animal waste is more common in the backcountry, but on highly-trafficked trails less experienced backpackers may leave their own waste too close to water sources. Untreated water in higher population cities and underdeveloped countries often have more human waste. (Gross, but true.)

The pathogens found in water sources are split into three groups:


Protozoa sounds epic, but it’s actually the most common problem you’ll face in untreated water. It comes in two forms: Giardia, which you’ve probably heard of, and Cryptosporidium, which you probably can’t pronounce. Both are parasitic organisms commonly found in streams, rivers, lakes, and ponds; and both cause gastrointestinal illness, like cramps, diarrhea, and vomiting.


Giardia has an artistic side, too! Courtesy the Center for Disease Control.

Giardia is easier to treat than cryptosporidium, but both protozoa can be eliminated by most filters, purifiers, and treatment systems.


Bacteria is gross, and pretty common in backcountry water. Common bacterias found in streams and lakes are Dysentery, E.coli, Salmonella, Shigella, and Campylobacter, all of which destroy your digestive track and give similar symptoms as protozoa.

Bacteria can also be eliminated by most filters, purifiers, and treatment systems.


Protozoa and bacteria should be avoided, but viruses are on a whole different level. You still end up with intestinal problems, but you can also get hepatitis or meningitis if the water happens to contain it. You really don’t want those.

The good news is that viruses are much less common in U.S. water sources, especially in the backcountry. They aren’t found in high, provable levels in the streams and lakes you might drink from, so if that’s your primary destination you don’t have to worry too much.

However, you will have to protect against them when traveling internationally, especially in underdeveloped areas. The bad news is that most filters for the backcountry do not get rid of viruses, so you might need another unit if you travel abroad.

Is There a Difference Between Filtered and Purified Water?

The pathogens above are either removed from water, killed, or rendered ineffective by filtration or purification. Each method and the corresponding device has its upsides and downsides, and you’ll end up making a specific choice depending your specific needs (as it always goes with gear).

The first consideration is if you need the water to be filtered or purified, which begs the question: is there a difference between filtered and purified water? Yes. The two are not the same, and it’s critical to know the difference.

Water Filtration

Water filtration to remove pathogens is how any other filtration process works: you need a device that blocks the pathogens while simultaneously letting water through.

hollow fiber membrane sawyer difference between filtered and purified water

Image courtesy Sawyer, All Rights Reserved.

You can’t see pathogens with your naked eye, but they’re there — dangerous little blobs bobbing around, waiting to wreak havoc in your belly. Filtration systems are sized to effectively block these pathogens.

However, as I said above, the majority  of the time filtration only works on protozoa and bacteria. These organisms are larger than viruses, and therefore easier to block with a filter.

Filtration is the most common route for U.S. backpackers because it’s what they’re commonly up against. The devices for filtering water are offered in a massive array, which I’ll detail below.

Water Purification

Purification takes it one step further. To be pure is to be free of contamination (or to have really good intentions) and water purity is important to international backpackers or those who want to be extra cautious.

Water purification takes care of the viruses, which are typically too small to be blocked by filtration. While purification can be done with filtration, it’s mostly done through chemical treatment or sterilization. When looking for something that tackles viruses, seek out the words “purifier,” not “filter.”

Backpacking Water Treatment Systems

To filter or purify is the easiest question to answer in the water treatment equation. How you will filter or purify is where the gear-junkie rears its obsessive head.

Water treatment is not a new concept. There are tried and true methods of purification from the 1970’s and earlier, but, as with all technology, advancements have been made in size, efficacy, and weight over the years. You can find a filter or purifier that fits your exact needs at a precise cost. You can filter for group or solo trips. You can burn off pathogens with magic wands or hunker down like an outdated safari-hunter and sip from the stream itself.

Backpacking water treatment systems abound; let’s dig into them.

Boiling Water

I’ll start with the most basic and boring of the bunch. Before there were giardia-filled waters there was the option to boil water. You have always been able to do it, and will always be able to.

The beauty of boiling water is that it works consistently and isn’t hard to remember. As the CDC says, keep your water at a “roiling boil” for a minute and you will kill off any protozoa, bacteria, or virus. It needs to boil for three minutes if you’re higher than 6,562 feet. Roiling boil means when there are solid plumes of bubbles rising from the base of your pot.

water-filter-and-water-purifier-boiling water Backpacking Water Treatment Systems

These bubbles must jet to the top for a “roiling” boil. Image by Indi Samarajiva via Flickr.

Boiling water is purification.

The Pros

The Cons

Chemical Water Treatment

Chemical treatment has not been around as long as boiling water (since humans found fire), but it’s considered the old-school, tried-and-true method. This means dropping tablets or drops into a container of water, shaking it around, and waiting the appropriate amount of time until all the pathogens are dead. Yes, you’re drinking dead pathogens.

water-filter-and-water-purifier-iodine-tablets Backpacking Water Treatment Systems

That yellow/green tab is iodine. It tastes gross and will discolor your water. It also will keep you from getting sick.

It’s important to note that chemical treatments, which I’ll list below, are something you should always carry as a backup. They have a decent shelf-life, work without any extra elements, and have no “pieces” that can malfunction.

Chemical treatment is purification.


The old-school chemical treatment for backpackers is iodine.



Chlorine Dioxide Water Treatment

Similar to Iodine, Chlorine Dioxide is a more modern chemical treatment for killing pesky pathogens. It often comes in the form of drops, and most commonly can be bought in the two-drop solution by Aquamira.


Chlorine Dioxide has similar pros to Iodine, namely: weight, cost, ease of use, and shelf-life. It also…


Pump Filters

It’s time to dig into more robust physical products. The first is one you’ll see all over the backcountry: pump filters.

A pump filter is typically made of three components:

  1. The hand-held pump
  2. The filter
  3. The tubes

You place the “dirty” tube in the water source, you pull and press the hand-held pump up and down, it brings water through the filter, and the water comes out the “clean” tube or directly from the filter into your water carrier.

water-filter-and-water-purifier-pump-filter-3 Backpacking Water Treatment Systems

This pump filter has one tube that goes in the water, and a spout on the bottom where it comes out. It also screws onto wide-mouthed bottles.

Depending on the specific model, a pump filter can be a filtration or a purification device. The large majority of pump filters are filtration, as opposed to purification. This is because the majority of pump filters use filters with holes that are too big to stop viruses from getting through. The MSR Guardian Purifier is a standout exception to this.



Squeeze Filters

Squeeze filters are a fairly new water treatment system to the backpacker scene, but they are overwhelmingly popular due to their ease of use and compact size. These things are tiny.

Pioneered (and dominated) by Sawyer, a squeeze filter consists of a bag, the compact filter unit, and your mouth (or another bag). It works by physically squeezing the dirty water in one bag through the filter and into whatever receptacle works best for you.

water-filter-and-water-purifier-squeeze-filter Backpacking Water Treatment Systems

Squeeze filters are simple and satisfying, but the flow rate isn’t the best.

Squeeze filters, at the time of writing, are all filtration based and do not purify water.



Gravity Filters

Gravity filters are new to the scene and have become increasingly popular, especially for backcountry trips with more than two people. The premise is to harness gravity to do all the “work” of filtering — the same “work” that’s all about the brawn with a pump filter.

You typically have two large bladders (two liters or four liters), multiple hoses, the filter unit, a carrying case, backflushing tools, and small attachments for water bottles or inline attachments. You fill one bladder with dirty water and hang it on a nearby tree or tall rock. You attach the dirty hose to the filter, then attach the clean hose to the filter, then attach the clean bladder to the hose.

water-filter-and-water-purifier-platypus gravityworks

Gravity at its finest wit the Platypus GravityWorks water filter.

You sit back as gravity moves the dirty water through the filter, treating your water while you relax. Sounds nice, right?

Gravity filters, for the most part, provide filtration, not purification.



Straw Filters

This is a baby category, one that safari-happy tourists in underdeveloped nations tend to use. It actually utilizes a very similar filter to the squeeze category, but instead of attaching a straw or bladder to the filter and squeezing, the filter is the straw.

You bend down to the water’s edge, stick the straw in, and suck. There’s your filtered water.

water-filter-and-water-purifier-straw-filter Backpacking Water Treatment Systems

Cool looking, maybe not the most convenient way to filter water.

Straw filters are often filtration devices, rather than purification, except for some high-end models.



Water Bottle Filters

Perhaps the newest rage in the filtration and purification world, water bottle filters are gaining traction among international travelers and more casual users. The filter is fastened to the inside of the bottle; every time you take a drink it is filtered on the spot.

This is similar to the straw filter and the squeeze filter, but in a water bottle form factor.

water-filter-and-water-purifier-water-bottle-filter Backpacking Water Treatment Systems

A water bottle filter with a soft container. Excellent flow rate, compact package.

Water bottle filters are a mix of filtration and purification, so you’ll want to know which kind you’re getting.



Ultraviolet Purification

The final water treatment method in this list is a major one: UV purification. This works by blasting ultraviolet light into the questionable water for a specific amount of time, which neutralizes the pathogens in it.

One big note about UV purification: It does not kill the pathogens. Instead, it scrambles them so they cannot reproduce, thereby causing them to be harmless to your body. This is true unless the water sits for hours, in which case they can “come alive” again and wreak havoc. Don’t sterilize large batches of water you don’t plan to drink until later on.

UV light is purification, as opposed to just filtration.



What is Micron Size for Water Filters?

As you can see from the above list, “filters” are the most proliferous water treatment method, and they’re often the most popular among backpackers, hikers, and campers.

With most filters you’ll see a number come up: micron size. This is how large the holes are in your filter, and therefore what pathogens will be stopped. Bacteria and protozoa are, at a minimum, .2 microns in size. You’ll see many filters  this number, or .1 microns, which is even smaller.

Viruses have a size of around .02 microns, which is significantly smaller. Very few filters can filter viruses, which is why UV light, chemical treatment, and boiling water are still the most effective methods of treatment for viruses.

What are Filter Media for Water Filters?

The filter media is the type of filter in the unit itself. This can determine water taste, filtration rate, cost, and a number of other factors. For most users the difference is not consequential, but here are the most common filter medias:

While you could choose a filter based on its media, I don’t think it’s necessary to get too specific.

Extra Water Filter and Purifier Features

There’s a ton of information above about water filters, purifiers, treatment systems, and use in the backcountry. There are a few things I haven’t covered yet, so I’ll go over them here.


Mentioned above, a prefilter is a device that helps to strain out particulate or sediment in water. It’s highly recommended if you’re pulling from silty, gross, or very shallow water. Particulate tends to clog filters, disrupt UV and chemical purification, and generally be a bummer.

Nobody wants little clumps of who knows what in their drinking water.

A prefilter gets rid of this. Many pump filters have one built in, which is handy. However, no other method has a built in solution.


The white screen is an automatic prefilter on this pump filter. A bandana will do, but it’s more labor intensive.

The first rule of thumb is to pull from the “cleanest” part of the water source. Grab water from the top of the pond without disturbing the water, or dip frequently until you get a clear batch.

You can usually buy a separate pre-filter unit for your specific filter, but it’s a drag to buy more for something that already works. I use a t-shirt or bandana to prefilter in necessary situations — I know it sounds silly but it works.

If you know your water sources will be full of crap, bring an appropriate prefilter.

Activated Carbon

Another element in some filters, activated carbon helps to get rid of unpleasant smell and taste. Found in higher-end filters, this is excellent if you are dainty about your water.

Number of Uses

The final element here is a big one. Number of uses applies to every water treatment type listed above and varies for each one, especially per brand. This makes it hard to say definitively that one type of filter has “more uses” than another.

In general, know the number of uses you’re getting out of your filter options.

Backpacker Types

So, with the entirety of water treatment systems above, which is best for you? I’ll go over water treatment in regards to our Backpacker Types below.

Note that the chemical treatment method is one I always recommend as a backup. It’s an excellent, foolproof backup for emergency situations in the backcountry. A vial of tabs or drops weighs under 3 ounces, can be used in a pinch, and will filter all pathogens.

However, due to its long wait times, I also recommend investing in a quicker water treatment system that works for you. These are discussed below.

Lastly, water treatment systems cost varying amounts. We found that the more you want to spend, the more people the system can treat (to a degree). Our recommendations reflect this.

Wilderness Backpacker

The Wilderness Backpacker needs a treatment system that is lightweight, easy to use, and can treat for small groups of people. In the U.S. viruses are not common in the backcountry, so a filter is all you should really need (especially if you have a chemical backup for purification).

For the Wilderness Backpacker we recommend squeeze filtration for its versatility in solo or two-person groups, a pump filter for its durability and small groups, and a gravity filter for ease of use and larger groups.

Ultralight Backpacker

The Ultralight Backpackers’ main concern is weight, and filters have a huge range when it comes to both size and weight. There are excellent filters that weigh almost nothing, so it’s easy to find a filter that will work with your ultralight setup. If you’re hardcore you can forego a filter and just use chemical treatment; this is always lightweight and works. However, it takes a while to filter water, which is also against the ultralight ethos (fast and light).

For Ultralight Backpackers we recommend minimal squeeze filters or UV purification. Both are incredibly lightweight, simple to use, and quick.

Car Camper

Car Campers in the U.S. don’t often need a water filter. Most state and federal run sites have potable water on site, which makes treatment relatively unnecessary. However, you may want to drink from the local stream. You can do this with chemical treatment, but filters are great for the group. Weight is not a concern, whereas high volume of water is.

We recommend a fast pump filter or a gravity filter for a Car Camper.

Day Hiker and Urban Hiker

Day Hikers in the U.S. probably don’t think about bringing water filters with them; but hiking in undeveloped nations, or in emergency situations, they are critical. This is also true for Urban Hikers. In both cases you need something easily portable, easy to use, and capable of purification.

We recommend water bottle filters, UV purification, or a very high-end pump filter for both Day Hikers and Urban Hikers.

Affiliate Policy: We support the hours that go into our reviews, testing, and guides through affiliate commissions on purchases made through links in this article.


6 responses to “Water Filter and Water Purifier Guide

  1. Sebeqsays:

    Does it make sense to use both methods, for example put dirty water in a bottle, put Chlorine Dioxide tabs to purify it and then after half an hour drink it with a squeeze filter?

    Does it make sense, would it purify the water and also get rid of other particles from the water?

    1. It’s unnecessary to do both methods if you have a proper squeeze filter. The Sawyer Squeeze, for instance, is rated to 0.1-micron absolute filtration, meaning that it will remove 99.99999% of all bacteria and protozoa, and it also removes 100% of microplastics. That’s virtually as perfect as a filter or chemical solution can get.

      Now, you can add in the Chlorine Dioxide as an extra preventative step, but it really isn’t going to result in any better purification because the Sawyer Squeeze is already fully capable of water purification on its own.

  2. It’s interesting to learn about different types of water filtration systems and how they treat contaminated water. My cousins and I are going camping in two weeks, and we’re interested in buying a water filtration system to help us survive in the wilderness. Thank you for the information on UV purification and how it neutralizes the bacteria in water.

  3. I like that you said that having proper water filtration could help implement healthy safe water consumption. Yesterday, my best friend told me that he and his wife were hoping to find a house water filtration that could provide health-safe water in their home to prevent having health problems. He asked if I had any idea what would be the best option to do. Thanks to this informative water consumption guide article for effective planning. I’ll tell him it will be much better if he consults a house water filtration service as they can help provide details about home water treatments.

  4. Water purity is not something to be taken lightly, and I appreciate this article’s focus on the importance of water purification, especially when it comes to safeguarding our health during our travels. Thank you for shedding light on this important topic. It serves as a valuable reminder to prioritize water purity and safety during our travels.

  5. I’ve personally been using a minimal squeeze filter for my backpacking trips, and it’s been a game-changer. The convenience and speed of the filtration process make it an ideal choice for those who value a fast and light approach. It’s reassuring to know that there are options like UV purification as well, offering simplicity and efficiency.

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