Here’s Your Best Water Purifier for Backpacking (It’s Not a Filter)

I’ve always hated water filters.

I backpacked the entire Appalachian Trail, John Muir Trail, and Colorado Trail with a filter.

I did hundreds of miles in the Grand Canyon with a filter.

I fussed with hoses.

I pumped. I squeezed.

I hated it.

There had to be a better system.

Water Purification Should Be Easy!

It’s often challenging to find the right backpacking equipment – we can love our gear a little too much. I’m sorry if you’ve wasted precious, irretrievable moments of your life weighing the pros and cons of such things as filter life, pore size, flow rate, and so on.

All I want is to have clean drinking water when I’m out on a hike.

But now there’s so many purification methods! What should I pick? Should I use a squeeze filter? A gravity filter? A pump filter? An integrated bottle? One of those cool looking straws?

How about none of the above.

I’ve tried many and seen them all, and I think chemical treatment is the best water purification system for backpacking. To be more specific, Aquamira drops are my favorite method.

If you’d rather use a good-old filter, all the best alternative systems are listed near the end of the post. Happy hunting.

3 ADVANTAGES of Aquamira vs Filters

If you’ve ever backpacked with filters, then the advantages of chemical treatment should be clear.

Here’s 3 advantages that Aquamira has vs filters:

1) It’s Quick and Easy

No hoses.

No squeezing.

No pumping.

If you’re hiking with others and stop to do a refill at midday, then you’ll be the first one finished dealing with your water. If you do the first premix step with Aquamira (Part A and Part B) before actually stooping to fill your containers, it’s virtually guaranteed.

By the way, here’s a little pro tip. Keep the items that you plan to use throughout the day (such as your water treatment method and snacks) easily accessible. Don’t bury them deep in your pack.

2) It Feels Natural

I think what I love most about using purification drops is that I can dunk my water bottle directly into the source. It feels more in touch with the wilderness – a total benefit.

Other systems are more physically separated from the actual water source. With drops there’s no worry of cross-contamination from the “dirty” water of various hoses and plastic sacks – no mechanical boundary between me and that rushing mountain stream. All the water in every container will ultimately be “clean” water.

3) No Maintenance

Most other systems require a degree of maintenance. Often you’ll have to clean out the filter when it gets clogged, or replace it entirely.

If you’re on a cold weather trip, sometimes the residual moisture in your filter can freeze, rendering it temporarily useless.

3 DISADVANTAGES of Aquamira vs Backcountry Filters

There’s a few disadvantages in this method of water treatment.

1) Physical Matter is not Filtered

This is probably the biggest downside to chemical treatment, especially for novice backpackers. There is no actual filter with Aquamira, so you’re going to get bits of dirt (and sometimes even small bugs) in your drinking water. Yuck.

So yeah, that will understandably turn a lot of people off, especially as you research backpacking gear from the comfort of your home. But once you spend time in the field and get a little more experience, bits of dirt become inconsequential as you realize backpacking is a dirty business, regardless of your best efforts to stay civilized.

Shallow and Murky Sources

What if you’re severely dehydrated, and your only source is a shallow, murky, moss-covered puddle? This is a valid concern, and one that I had when I first switched to chemical treatment.

In desert environments like Arizona and Utah, there were occasions where I carried a filter or Lifestraw as backup, but here’s the thing: they never got used. On long trips (the Hayduke Trail and off-trail in Grand Canyon), I’d leave behind the backup filter after the first few weeks. It simply never got used.

Shallow sources can sometimes be frustrating, especially if you rely on something with a narrow mouth like Smartwater bottles. You can negate this problem by taking the time to find a micro-location with optimal leverage to tilt your bottle upward. In a worse case scenario you can use you cookpot as a filling device, or get creative and use a ziploc or bandana.

2) You Have to Wait a Few Minutes

Another disadvantage is that you have to wait for the chemicals to activate. The Aquamira directions say to wait 15 minutes, or longer in cold weather. So as a general rule I will wait 30 minutes if I can, or at least 20 if I’m really thirsty.

Once you spend more time backpacking and grow familiar with dialing in your needs, this is really a non-issue. In over a decade of use, I can’t recall a single instance where the wait-time was a problem.

Note that Aquamira can take up to 4 hours to kill Cryptosporidium.

Ultra-Runners and FKT Seekers

For obvious reasons, the activation time could definitely be a problem for ultra runners – anyone in a race or trying to set a record. With a squeeze filter you can simply scoop up the water and squeeze it out immediately, even directly into your mouth there at the source.

Since drinking at the source is definitely more efficient (weight-wise) than hauling your water up the trail, some ultralight hikers may take issue with chemical treatment, too.

3) Chemicals Aren’t… Like… Natural, Dude.

This complaint usually comes from hippies from California that reek of essential oils, but I get it. Consuming such chemicals on a regular basis might give you some pause, especially on a thru-hike or an extended trip.

My rebuttal to this argument is that your municipal water at home is treated with chemicals, too. In many cases it’s treated with chlorine dioxide, the same solution that’s used in Aquamira. Maybe you’re lucky to live on a property with its own well, or have a reverse osmosis system at home. But even in that case, the great majority of us end up consuming a lot of water that’s minimally filtered (if at all) after it leaves the tap.

You’re out backpacking, experiencing the world. Live a little.

Aquamira is Good & Safe – Here’s How to Use it:

Aquamira comes with a “Part A” and a “Part B.” For each quart of water, you mix 7 drops of each “Part” into the plastic bottle cap provided for mixing. It takes about 5 minutes for the solution to do its thing.

Then you take your water bottle and fill it directly from the water source. If you’re using a bladder (like a Camelbak), you can just hold the bladder open in one hand, and fill it via a bottle from the other hand.

Then you pour the Aquamira solution into your water.

Wait 15 minutes, and voila, you’re free to drink. If you want to be extra careful, you can gently loosen the lid of your bottle and pour some water out to flush the threads.

Treatment Instructions

Here’s the Aquamira drops directions pulled straight from the packaging:

1. Prior to treatment, clean and disinfect the water storage container and lid.
2. Place 7 drops Aquamira Water Treatment (Part A) and 7 drops Phosphoric Acid Activator (Part B) in a cap to pre-mix.
3. Let mixture react for 5 minutes to ensure full activation.
4. Fill container with 1 quart (1 liter) water. Add contents of mixing cap.
5. Shake or stir and let stand for 15 more minutes. If water is very cold or turbid, let stand for 30 minutes.
6. Water is now ready for use.

It is a violation of Federal law to use this product in a manner inconsistent with its labeling.

Personal Notes about the Directions

Rather than using 7 droplets as instructed, I tend to use 8. This is because the directions (above) are designed for one quart, whereas most of my containers tend to be one liter.

Also, in the case of a narrow-mouthed Smartwater bottle, there’s always going to be a drop or two of the pre-mixed solution that you just can’t seem to shake loose from the mixing cap into your bottle.

To eliminate that effect, when I have a wide-mouthed Nalgene or a Camelbak, I’ll simply dunk the cap into the top surface of my water to ensure that all of the pre-mix solution is put to good use.

It’s also worth noting that you’re not limited to pre-mixing only a single quart at a time. For example, I’ll treat my 3-liter Camelbak with anywhere from 21 to 24 droplets of both Part A and Part B in one fell swoop. Do the math and apply the appropriate multiples for larger bulks of water.

Aquamira Ingredients and Labels

The active ingredient for Part A is 2% Chlorine Dioxide. The remaining 98% is listed as “Other Ingredients.”

The active ingredient for Part B is 5% Phosphoric Acid. The remaining 95% is listed as “Other Ingredients.”

Shelf Life and Leaking

Each individual bottle will have a listed “lot number” and expiration date. The date will be 4 years after it was manufactured. The phosphoric acid in Part B is stable, but Part A will begin to degrade due to environmental factors after you first open it.

I’ve had old Part A bottles that acidified after being stored for too long, but have never had a problem with unopened containers. I’ve also never had a bottle acidify or leak in the midst of a long trip.

When you combine the Part A and Part B in the mixing cap, the solution turns into a deep yellow color in 5 minutes. It’s said that Aquamira is still effective (and has not expired) as long as the deep yellow color is still achieved.

Parasites, Bacteria, and Viruses (Effectiveness)

Aquamira (chlorine dioxide) kills Giardia, Cryptosporidium (both protozoan parasites), bacteria, and viruses. It’s said that Giardia and Cryptosporidium alone are the culprits of 80% of waterborne illness. A study even found that chlorine dioxide was more effective against viruses than household bleach (sodium hypochlorite).

Regarding Cryptosporidium, however, it’s worth noting that Aquamira can take up to four hours to kill it. So even though its technically effective, in most practical scenarios you will not be eliminating these guys.

I’ve never gotten sick when using Aquamira water treatment on my backpacking trips.

Cost & Availability

Aquamira drops are not available in bulk, at least not in the traditional sense of the term. Backpackers should be fine with the 1 ounce bottles, which last a long time (the manufacturer claims 30 gallons). Two-ounce containers are sometimes available, which may be considered a “bulk” size. You can also get a 4-pack of 1 ounce containers.

The 1 ounce bottles are usually sold for $15.

Aquamira is Made in the USA.

Variations

Aquamira was traditionally sold in square bottles, but in recent years the company has moved to a round design. I personally preferred the square version, and hope that they move back to this style soon. For what it’s worth, in late 2022 the REI site still has the square version pictured, but Amazon shows the updated round bottles.

There’s also new glass bottles available with droppers built into the caps, but I haven’t tried these yet.

What’s in the water?

Here’s the bad guys that we worry about in our drinking water:

• Parasites (protozoa such as Giardia and Cryptosporidium)
• Bacteria (Campylobacter Jejuni, E Coli, Salmonella)
• Viruses (Norovirus, Hepatitis A)
• Heavy Metals (Lead, Arsenic, Copper)

There is a lot of pseudoscience and hearsay regarding the actual safety of drinking straight, untreated water in the wilderness. Some backpackers will report “never” or “rarely” treating their water with no ill effects, crediting their luck to the wise choice of only using high elevation sources where “you can see where the water comes out of the ground.”

For what it’s worth, ALL of the pathogens listed above have instances where its possible to carry the pathogen but have no symptoms.

I’ve tried the method above with some success, in fact using no water treatment at all on my thru-hike of Vermont’s Long Trail. I did finally get sick near the end of the 26-day trip, but only briefly. It’s also a tradition for me, whenever I’m there, to drink a straight liter of water from a place in the Grand Canyon called Thunder River.

What Actually Makes You Sick?

Continuing the topic of pseudoscience and anecdotal evidence, the specific pathogen that’s causing your explosive diarrhea is often unknown. Symptoms often mimic each other, and doctors will make their diagnosis based on surrounding evidence. For example:

“You’ve been backpacking and now you have consistent, aromatic, greasy diarrhea (sorry) with heavy bloating? That sounds like Giardia. Here’s some Flagyl.”

“You’re on a rafting trip, and the majority of the crew came down with diarrhea, vomiting, and even a light fever? NOROVIRUS!!!”

And so on. My point here is that in the great majority of cases, your doctor isn’t taking a stool sample and sending it off to a lab to pinpoint whether its actually Giardia or E Coli that brought you into the clinic. Infer from all this what you will.

How to Purify Water in the Wilderness

Here’s a list of general guidelines for purifying your backpacking water:

1. Bacteria is probably the most common pathogen found in backcountry water sources. It tends to be washed in from feces – cows, wildlife, hands of previous hikers, furry friends, etc.
2. Next is Giardia. It’s most often found in areas with high beaver populations. Cryptosporidium is possibly just as common.
3. Viruses are less common in backcountry water sources, but still sometimes occur. Person-to-person transmission is more frequent, like sharing that bag of trail mix or cross-contaminating things on a group rafting trip.
4. Heavy metals can also be in the water. Most of them won’t immediately make you sick except for rare, high doses, but they can have long term effects.
5. It’s best to drink water that’s at a high elevation relative to its surroundings, has some flow, and has a visible source (spring).
6. Big rivers and large, low-lying lakes are most likely to be contaminated.
7. UV rays will eventually kill most pathogens, so surface water in direct sunlight can be ideal.
8. High-traffic sources on busy trails are more likely to be infected.

For more about what’s in all that water out there, and what can actually make you sick, check out this report for further reading.

More Water Purification Methods: An Overview

The various methods of purifying your drinking water on a backpacking trip can be broken down into 2 essential categories. These are filters and chemical treatment.

A third category technically exists in treatment with ultraviolet light, but this tends to be mistrusted despite its scientific effectiveness. The 3 main drawbacks of UV treatment are its failure to remove physical particles (also a drawback of Aquamira), reliance upon electronics (batteries), and perceived user error. If you’re still interested, check out the Steripen.

Below you’ll find brief reviews of the best backpacking water purifiers available today. The term “purifier” technically refers to a system that reliably kills viruses (as opposed to filters), but the words are often treated as synonyms, so there you go.

Filters

The heart of most filter systems consists of a fibrous material – essentially a heavy-duty coffee filter. It has small pores that are measured in a term called microns. Smaller micron numbers catch more material.

Viruses are too small to be caught by most filters, so filters alone will not protect against viruses.

The mechanics of different filters are the major thing that sets them apart from each other. The four types of force you use to push water through a filter are:

• squeezing
• gravity
• pump action
• suction

When used properly, all of these filters below are generally safe for backpacking. Most filters will not eliminate viruses from the water, but viruses are usually of little concern. It’s thought that protozoa and bacteria are the main culprits of illness.

1) Squeeze Filters

Squeeze filters are the most popular type of overall water treatment used on the trails today, with the Sawyer Squeeze lineup being the most popular among them. If I were to regularly use a filter versus Aquamira, it would likely be the classic Sawyer Squeeze model, as opposed to the “mini” and its other variations.

Squeeze filters are most ideal for solo hikers.

A close runner-up to this choice would be Platypus Quickdraw Microfilter System. As a third choice, I like the durability and convenience of the Lifestraw Peak Squeeze.

2) Gravity Filters

Gravity filters don’t require any effort to push the water through the sieve, but you will need a sturdy tree branch or something else in the environment to rig the system. Most gravity setups have a designated “dirty” bag and a “clean” bag, with an inline filter set up amid the hose that connects them.

These systems are most ideal for large groups using an ample water source. The Platypus GravityWorks is far and way the most popular gravity filter, with the MSR Autoflow coming in second.

3) Pump Filters

Pump filters are the old tried-and-true method of purifying water, earning me those ripped biceps so on the Appalachian Trail 20 years ago, so I looked less like a T-Rex… in my own mind. The classic model in this case is the Katadyn Hiker, with the ceramic MSR MiniWorks worthy of a mention, too.

Also falling under this category is the MSR Guardian, which is an absolute beast of a filter that’s ready for the apocalypse. What’s awesome about the Guardian is that it’s advertised to be SELF CLEANING, and its technology blocks viruses too – a rare feat in backpacking water filters. The Guardian is available as a gravity filter, too.

Pump filters are best for pulling water out of shallow, gross puddles.

4) Suction

This type of inline filters is made to be attached to the water bladder you’d normally carry on a hike. For example, if you use a standard Camelbak or Platypus bladder, these filters are made to fit between the bladder and the suction hose that you’d normally drink out of.

The benefit here is that you can just fill your bladder, re-pack it, and go. The drawbacks are that you need to filter all your water through the hose (or carry a secondary purification system) and sacrifice your bladder as a “dirty” bag. The overall setup strikes me as a little clunky, too.

The most popular of these is the MSR Thru-Link.

Years ago, the Lifestraw brand was built upon what’s basically a beefed-up straw with an internal filter. It works just fine and can be neat to have around for emergencies, but overall it isn’t very practical for backpacking.

Filtration Bottles

Finally, it’s worth mentioning that there’s numerous bottles on the market that have filters built into them. These might be ideal for an endurance athlete looking for convenience, or maybe for a weekend warrior in a wet climate.

Chemical Treatment

Chemical treatment is great for eliminating the pathogens you’ll find in water (including viruses), but fails to weed out particles like dead bugs, moss, and heavy metals.

Chemical treatment includes chlorine dioxide (Aquamira), iodine, and even household bleach. It comes as a liquid or tablets.

Iodine is the original, old-school backpacker’s chemical treatment of choice. When I first started backpacking, I carried a pump filter and brought along some iodine as backup. Iodine is notorious for its unique flavor, despite that it often comes with “neutralizing tabs” to soften the taste. This is how Kool-Aid so often found its way into backpacker’s kits in the 1970s.

Every once in a while you’ll encounter a hiker that uses plain-old unscented Clorox bleach. These backpackers will simply transfer some bleach to a designated carrying container (like a Visine dropper), and add 1 droplet of bleach per 16 ounces of water. Wait 30 minutes and voila… supposedly. I mean… this sounds logical, but I never had the courage to try it.

Here’s how Aquamira compares to other chemical treatments:

Aquamira vs Potable Aqua (Iodine)

The Potable Aqua brand manufactures the classic iodine tablets discussed above. Iodine is almost as effective as chlorine dioxide, known to kill protozoa, bacteria, and viruses. Iodine does not kill cryptosporidium, but Aquamira takes up to four hours to kill cryptosporidium anyway, so there’s little difference there. The main differences are that iodine is said to be “less effective” against giardia than chloride dioxide, plus the yuck taste of iodine.

Potable Aqua also makes chlorine dioxide tablets. The main difference here is that each tablet is designated to treat one quart of water, so Aquamira drops are more versatile for treating different amounts. Aquamira is also more cost effective than tablets.

Aquamira vs Micropur (Katadyn Tablets)

The Katadyn brand also makes chlorine dioxide (Micropur) tablets. The differences here are the same as those mentioned for the Potable Aqua tabs, above. Aquamira is more cost efficient and is better for treating varying quantities of water.

Tablets are Ultralight

For the weight conscious backpacker, however, tablets are often a lighter option than liquid for shorter trips. The 2 required (full) bottles of Aquamira weigh about 3 ounces, so the weight of a few Mircropur or Potable Aqua tabs is the clear winner in this regard. It can also be difficult to gauge how much Aquamira is left in a used bottle, requiring you to carry a backup and further adding to your weight.

Aquamira vs Bleach

Aquamira is better at killing Giardia and Cryptosporidium. Household bleach (sodium hypochlorite) will kill bacteria and viruses (same as Aquamira), but it will not kill the aforementioned parasites. Personally, I also tend to trust a product deliberately manufactured to treat drinking water, as opposed to repurposing some Clorox from the laundry aisle.

Remember, You Can Always Boil it Instead

A fitting way to wrap up this article is to remind you that you can always purify your water by simply boiling it. The general rule is to get it to a rolling boil for one full minute, or 3+ minutes for elevations of 6,500ft and above. This should kill all the pathogens in the water, but it will not eliminate heavy metals.

If I’m camped near my water source, I often won’t treat the water I’m using for dinner or morning coffee.

I am not affiliated with Aquamira – it’s just what I like to use.

I buy all my own gear, like you.