Tutorial: Methods to purify backcountry water || Pros, cons & my picks

There was little doubt if I needed to purify the water from this stock tank on Arizona’s Coconino Plateau.

Earlier this month there was a healthy online debate over the true risk of drinking water from backcountry sources without purifying it first. I appreciate that Ethan Linck brought up the topic and agree that many sources are safe to drink without treatment. But I agree more with Wes Siler and Christie Wilcox:
  1. It’s difficult to be certain of the contamination risk, and
  2. Waterborne cooties can be uncomfortable (understatement).
  3. So, as a general rule of thumb, just purify it.
Missing from their debate, however, was any instructional knowledge, specifically: I’m generally competent in explaining the how’s of backpacking, so in this two-part series I will try to fill this gap. If you’ve read The Ultimate Hiker’s Gear Guide, some of this text may sound familiar — it’s from the chapter on Water, which also includes discussion of contaminants and water storage. (A clause in my contract allows me to share short sections of the book.) If you haven’t read the Gear Guide, you should consider it: it’s filled with trail-tested advice, and almost certain to save you time and money.
A decomposing cow or steer in Harris Wash, Grand Staircase-Escalante National Monument. I had filled up my bottles below here and had purified the water, but thankfully didn’t drink any before encountering this.

How to purify water from backcountry sources

There are four basic techniques for treating water:

  • Boiling
  • Filtration
  • Chemicals
  • Ultraviolet light

Boiling is time-tested, but impractical as a regular treatment: it consumes time and fuel, and hot water is normally unsatisfying to drink. I rely on this method only when I’m heating up water anyway for meals or coffee.

The three remaining methods are available in a variety of form factors, and are better for routine treatment. There is not a single “best” water treatment method, even though some of my online peers will lure you with click-bait headlines that say so. Your specific preference will likely be a function of:

  • Group size,
  • Frequency and quality of water sources, and
  • Importance of time, long-term reliability, and cost.

Some treatment methods are labeled as a “purifier,” a distinction reserved for those that extract or kill all pathogens (i.e. protozoa, bacteria, and viruses). The same effect can sometimes be achieved by combining two non-purifiers. For example, filter and then chemically treat the water.

At a glance

This chart highlights and pros and cons of the various treatment options. Keep scrolling for a more in-depth discussion.


At a minimum, filters will strain out larger-bodied pathogens like protozoa and bacteria, as well as sediment, larvae, and other floaties. This should be sufficient for most backcountry watersheds, where viruses are rare.

Some filters go above and beyond, by removing chemicals and improving water taste. The MSR Guardian Purifier does all of the above, and even removes viruses. But its exceptional performance comes at a high price — it’s $350 and 17 oz.

Filters have other trade-offs, too:

  • They leak retained water.
  • Their flow rates are slow to begin with, and get worse until the filter is backwashed, scrubbed, or replaced. And,
  • Most cannot be operated on the move.

Specific filter types have additional considerations:

Pump filters

Pump filters like the Guardian are my least preferred treatment technique. In addition to being the heaviest option, their operation involves considerable effort. Pumping large volumes of water is downright tiresome — imagine treating a few liters of water for you and several partners, at a typical flow rate of about one quart per minute.

Gravity-fed filters

Gravity-fed filters like the Platypus GravityWorks 4.0 ($120, 11 oz) are ideal for groups and extended camps. Simply suspend a reservoir of untreated water above an empty reservoir — using a branch, boulder, or steep slope — and return a few minutes later to a full reservoir of filtered water that can then be decanted into individual bottles.

A gravity-fed system, using the CNOC bladder and a Sawyer Mini. This system is ideal for groups and long camps. Simply suspend the dirty bladder on a tree branch or rock, and then decant the filtered water into individual bottles.

Inline filters

Inline filters like the Sawyer Squeeze ($40, 3 oz) share the same filter technology with gravity-fed filters, but rely on a manual force like suction or squeezing. With some inline filters, you can drink directly from creeks, pools, or bottles by using it as a straw. But it’s much easier to squeeze untreated water through it from a collapsible bottle.

Left to right: the original Sawyer Squeeze, Sawyer Mini attached to a 16-oz bottle, and the backflush plunger.


There are three chemical options, only one of which I would recommend. Note: If you expect floaties in your water, it is advised to bring a bandana or coffee filter in order to strain out large particles before treatment.


Iodline-based treatments like the classic Potable Aqua tablets ($7, 1 oz) are lightweight, inexpensive, and widely available, but they are not effective against Cryptosporidium and their overall
effectiveness is impaired by cold and turbidity. Your water will also taste like a medicine cabinet.


Household liquid bleach (sodium hypochlorite) would be a better home remedy than iodine. However, it degrades with age and it’s still slow against Cryptosporidium. Plus, it’s like drinking pool water.

Chlorine dioxide

Chlorine dioxide been used by municipal water treatment plants since the late 1940’s and is the superior chemical treatment. The tablet and droplet forms share identical technology, but only tablets like those from Aquamira ($10 for a 10-pack, 1 oz) have been approved by the Environmental Protection Agency as a “purifier.” The marketing copy for Aquamira drops ($15, 2 oz) claims only that they “kill odor-causing bacteria and enhance the taste of potable water.”

Fear not. A proper dose of chlorine dioxide (in tablet or droplet form) will kill most pathogens within 15 minutes, or within 30 minutes for very silty and contaminated (“worst-case”) water.  Cryptosporidium is more resilient, however: The recommended dwell time is four hours. Unlike iodine and bleach, chlorine dioxide has minimal chemical aftertaste, if any.

Aquamira tablets (left) and drops (right)

Ultraviolet light

UV treatments like the SteriPEN Ultra ($100, 5 oz) and similar products prevent all pathogen types from reproducing by scrambling their DNA. You still ingest the pathogen, but without offspring there should be no effect. Its speed — at about 90 seconds per quart — is attractive, but the technology has problems:

  • The cost and weight of replacement batteries adds up.
  • Narrow-mouth bottles like the Platyplus SoftBottle and smartwater 1L bottle cannot be used, because the light cannot be submerged to the required depth.
  • Its effectiveness decreases in turbid water (although it must be good enough to have earned the “purifier” label). And,
  • There are too many possible points of failure. The unit can break if dropped, stepped on, or stored poorly. The batteries die, and the battery compartment is not necessarily waterproof. And the electronics can be fickle.

For such a critical item, its reliability is discomfiting. If you go this direction, I recommend having a backup system.

My picks

For about 15 years my go-to water treatment method has been chlorine dioxide. It is the standard technique on my guided trips, too. The results have been excellent, and now statistically significant given the number of clients that have gone through my program — if it wasn’t effective enough, we’d have noticed by now.

I prefer Aquamira drops ($15, 3 oz), but in temperatures below about 15°F I swap to tablets because they don’t freeze. Versus tablets, droplets are more economical (at about 50 cents per gallon) and flexible, since I can easily modify dosages with proportional changes to dwell times. Especially when decanted into smaller dropper bottles, the weight is negligible.

Chlorine dioxide is transported as a two-part solution and must be mixed for five minutes before it can be dispensed into water. By storing premix in an airtight and opaque dropper bottle, this wait time can be eliminated. McNett, the manufacturer of Aquamira, discourages premixing due to potency concerns, but the practice seems to be safe with some degree of user education.

My go-to water purification treatment is Aquamira, in drop form. I bring a small “pre-mix” bottle that holds about of a day of treatment.

In recent years I have also warmed to the Sawyer Squeeze, which has the advantage of instant potable water. It’s ideal for wet environments and for backpackers who always purify. I recommend the original Squeeze over the smaller Mini, because its weighs marginally more but has a reliably better flow rate.

In group settings, the Platypus GravityWorks is worth mentioning. It’s effective, hassle-free, and very fast. The Squeeze can function the same way, when packaged in the Sawyer Gravity System.

The combination of chlorine dioxide and the Squeeze or GravityWorks may make the ultimate purifier combination. Use the filter to quickly filter small amounts, and the Aquamira to purify large quantities that will sit overnight or in your pack for several hours. For highly suspect water, use both methods.

How do you purify water, and why is that you go-to approach? Any tips or shortcomings to share? Leave a comment.

Disclosure. I strive to offer field-tested and trustworthy information, insights, and advice. I have no financial affiliations with or interests in any brands or products, and I do not publish sponsored content

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Posted in , on March 27, 2018


  1. garrett on March 27, 2018 at 4:09 pm

    I was an aquamire guy. but i dislike the 5 minute mixing and 15 minute purifying time.

    I switched to a steripen and its been great. all your concerns about it are valid except the bottle mouth size combatability.

    It works fine with small mouthed bottles because you can make a seal with the rubber below the light bulb and the mouth of the bottle and just shake it instead of stirring it.

    • Andrew Skurka on March 27, 2018 at 4:14 pm

      I think the compatibility may depend on the UV pen. The one I used years ago (and turned me off from UV forever maybe) would not even turn on because the sensors weren’t submerged, and there was no way to get the sensors into bottle.

      • Gement on March 31, 2018 at 10:50 am

        The sensors now work fine in a Smartwater bottle and the Ultra is USB-charged, removing the spare battery and battery case waterproofing concerns.

        While the technical risks of an electronic device with a glass bulb still exist, it might be worth updating the post with the current accurate information on those two points.

        (Also, *every* method disclaims that turbidity will make it less effective and that it’s only to be really trusted with clear water.)

  2. Dale Steele on March 27, 2018 at 5:05 pm

    Have you tried the Katadyn BeFree? It is similar to the Sawyer Squeeze but has significantly more water flow coming out of the filter. Filtering time is cut down considerably. Hydrapak bags come in a variety of sizes and the filter is interchangeable.

  3. Maeglin on March 27, 2018 at 5:41 pm

    I use a gravity system using a Swayer Squeeze, a 4L GravityWorks Dirty bag and 2L Platypus 2.0L Hoser. My first-aid kit contains small droppers of Aquamira for backup. The 4L dirty bag lets me filter for my family or my own dinner + breakfast + travel bottles all at once. The filter system weighs 6.8oz with 1.8oz more for two 1L sport drink bottles.

    My main complaint is that the GravityWorks bag does not seal well enough to carry water in the backpack. The spring loaded hose connector is also a concern because it could break.

    I had hopes for the CNOC bladder, because the filter attaches directly. I would like to be able to carry dirty water when I need more capacity. Unfortunately, the plastic closure piece slides off and the bag leaks even with it on. It is also heavier and only holds 2 liters.

    If anyone can point me to a lightweight dirty water bag that is water-tight and fits directly to a Sawyer Squeeze, you’d have my eternal gratitude.

    • Maeglin on March 27, 2018 at 6:35 pm

      I’ll add that two desired features in the dirty bag are a wide opening to fill quickly and some way to hang the thing. The whole system hangs unattended from a branch or my tent.

      CNOC came out with a new closure this month; I’ll let you know more after trying it.

      • Maeglin on May 23, 2018 at 11:34 am

        Update: CNOC sent a replacement plastic closure piece that is much tighter. I do not think it will slide off accidentally. My appreciation to them for their support.

  4. Randy on March 27, 2018 at 5:46 pm

    I was thinking of carrying both the Squeeze and Aquamira for the same reasons you mentioned. Nice to know I’m not just being a belt & suspenders goof. I haven’t tried this yet, but I was also thinking if I needed to treat, say two or more liters, the two together could actually save a little time and energy: the 5 minute mix can hang out while I push a liter through the Squeeze; then dump the Aquamira into another liter(s) for later and I’m off. Also I’ve seen filters fail and the drops are little weight for a backup.

  5. Brian on March 27, 2018 at 8:14 pm

    Link to that tiny black dropper bottle please

    • Andrew Skurka on March 27, 2018 at 8:44 pm

      Ha! You will have to ask Mike Clelland, who bought a hundred of them last year before our guiding season and distributed them to clients. I bet he probably still has a bin of them leftover.

    • Maeglin on May 23, 2018 at 11:47 am

      I tossed my first set of dropper bottles because they were not air-tight. Nalgene has perfected the design. I found it makes a difference with elevation changes and specifically on air flights.

      Try squeezing the air out, put on the cap and see how long the bottle stays sealed.

    • Ben on January 18, 2020 at 9:22 pm

      Litesmith sells them individually.


  6. Bob S. on March 27, 2018 at 8:50 pm

    I’m usually in more urban areas where chemical contaminates are a concern so I use a Sawyer Select S3.

    • Trevor E. on April 1, 2018 at 7:17 pm

      As someone who lives in the northeast US and works as an Environmental Engineer, your concerns are valid!

      • Bob S. on April 2, 2018 at 4:54 pm

        Yup, I live in northern New England. What some see as pristine forested conservation areas I see as former factory sites, paper mills, and farmland that had been stripped of trees where just about every toxic substance imaginable has been dumped, sprayed, spewed, or leaked.

        Anyone have any thoughts on whether the Sawyer Select S3 lives up to the claims that it can remove pesticides, chemicals, and heavy metals? I’m still in the testing mode and my opinion so far is it’s a pain to use and carry but probably better than most filtration systems when non-biological contaminates are suspected along with your typical garden-variety nasties. Still, I’m not brave enough to put the S3 through a vigorous test and I have only used it where other purification systems would be safe to use.

  7. Lisa on March 27, 2018 at 9:03 pm

    The Steripen Ultra is rechargeable via USB. No batteries. If you carry a way to recharge your phone, you can also recharge your Steripen. Fast, easy, tasteless & no chemicals. I’ve used it for 7 day trips & haven’t come close to depleting the battery.
    Aquamira drops as backup.

  8. Collin on March 27, 2018 at 9:33 pm

    Just wanted to share some thoughts that might benefit others. People seem to think that Aqua Mira is a slow or innaficient system compared to filtration. This is the method I used on my recent Arizona Trail Thru Hike. I was unsure about the safety premixing so I found a middle ground of sorts. I carried the same mini dropper bottle you show above. When I arrived at a water source I would drop in the required drops for the amount of water I was about to fill. I found that size dropper will hold about 2 liters worth of drops. (Your droppers may vary) If I felt like taking a break I would just wait the 5 minutes for it to react, or I would just keep hiking and when 5 minutes was up I would distribute the drops accordingly and continue hiking. 30 minutes later I had water to drink. If i needed to purify more than 2 liters I would just repeat the above process. Sometimes I would premix drops for the next source. If it was late in the day and I had water to drink I would just mix and add the drops in camp. Overall I loved this method and could never go back to filtering as a primary method. It took maybe 1 minute to mix the drops and another 20 seconds to add the drops to water. Compared to filtering which takes more time (and your flow rate only gets worse) and more effort. Also bladders can fail when squeezed. The downside of Aqua Mira is it can be expensive in the long run, and you have to replenish your supply every so often or carry several ounces. Hope this helps somebody! Thanks

    • Randy on March 28, 2018 at 9:45 am

      Premixing before next water source… that does sound like a happy medium. Good tip.

  9. Hunter Hall on March 27, 2018 at 11:54 pm


    I just threw this up on YouTube for this thread.

    I’m a bit embarrassed to admit how much time I spent on the system, which I find perfect for two people.

    The weight and versatility are unmatched in my opionion. It can be used as a gravity system and then converted into a hydration pack or the sawyer mini can be used with a smart water bottle while hiking.

    I bought all those individual pieces separately as platypus accessories. The dual bite valves are the key to the flow and different modes.

    I carry AM tablets as back up. I have no experience with the liquid drops yet…

    I only boil in winter or when that’s the only option.

    That’s about as nerdy as it gets gentlemen. 🙂

    • Andrew Skurka on March 28, 2018 at 8:39 am

      Blue Label, good choice.

  10. NTN on March 27, 2018 at 11:59 pm

    Sawyer sqeeze or mini, depending on duration of outing with chlorine dioxide tablets from MSR for a back-up should I suspect viruses are present. Also like to have tablets to disinfect my treated water bottle after I booboo by mistakenly putting untreated water in it. I rarely drink untreated water.

  11. Gement on March 28, 2018 at 7:18 am

    The only thing I would add is a discussion of prefilter methods; it takes some experimentation or instruction to figure out how to strain crunchy water in the course of getting it into the dirty water. I personally have settled on using my pot or, if expecting frequent muck, carrying a separate dirty water disposable gladware for pouring, but I keep feeling like there’s a better way I haven’t found.)

    Some heroic wonk on BPL once posted the results of straining swamp water through every membrane they owned, bandana, coffee filter, stocking, and several pack towels. The winner was the MSR Nano (now Packtowl Nano) for medium fast flow rate and very clear water. I dug that info up before I started hiking, so I just carry a chunk of that as my prefilter and I’ve been happy with it. They have been sitting on clearance at REI for almost a year.

    Found the thread! Thanks, Ken Larson! (Many other interesting ideas in there for people who want to really wonk out on it.)

  12. Max on March 28, 2018 at 7:59 am

    1 vote for bleach! A couple drops per liter and you can’t even taste it. Sawyer standard size squeeze filter too.

    Gotten giardia a couple times in Central America drinking untreated water and it’s not so bad if you don’t mind a distended belly and super gnarly sulphur gas coming out of two orifices simultaneously. Quick trip to the pharmacy clears it right up (if you can walk that far).

    • Gement on March 28, 2018 at 8:33 am

      For many folks, giardia is easily cleared up. For a non-negligible percentage of unlucky folks, it is treatment resistant; it settles in and lingers for years. Others have long-term negative effects from killing off their healthy gut flora with the industrial-grade antibiotics needed.

      Drinker beware.

      • Thomas on March 28, 2018 at 4:17 pm

        This is an important point, members of the population of backcountry water consumers will differ in their resistance/susceptibility to giardia. This is sometimes loosely referred to as “immunity”, which is incorrect in the narrow (and useful) meaning of that term.

        Since the reason for the difference in susceptibility is not understood, even for greater public health threats than giardia, there is no test to assess our individual susceptibility.

        Drinker beware indeed.

  13. Ken on March 28, 2018 at 8:31 am

    I don’t think you mentioned the risk of a filter freezing.

    I get tired of sleeping with batteries, I-phone, filter etc. and sometimes I forget. I contacted Sawyer once and they agreed there is no reliable way to test if the filter is functional.

    On that note, how do you know how long pre-mixed AM is good?

    • Andrew Skurka on March 28, 2018 at 8:37 am

      There is no reliable public data about the effectiveness of pre-mix. But in some off-the-record conversations with people who know about such things, 24 hours should be totally solid, 48 hours still pretty reliable. When you start pushing it to a few days, effectiveness drops, and beyond that it’s iffy. The key about pre-mix is that it must be stored in an air-tight and UV-impermeable bottle, because its effectiveness decreases rapidly due to both elements.

  14. Jake on March 28, 2018 at 2:12 pm

    Maeglin: I had the Platy bottle/Sawyer Squeeze compatibility issue as well. The threads are just different enough that you can’t reliably get a good seal.

    I switched to Evernew Water Carry System 2000 ml bags (look on Amazon) and the threads match *perfectly* with the Sawyer Squeeze in my MYOG gravity system. Plus I’ve found them to be more durable than the Platy bags.

    Downsides: they’re about 50% more expensive than Platy bags and they’re usually shipped from Japan, so order early. They don’t have a wide mouth, but I carry a SmartWater bottle with the top third cut off that I use as a scoop, which makes it easy to fill. Also doubles as a convenient case for my filter/tubing when they’re not in use.

    As far as hanging, I used a grommet kit to add four grommets to the bottom of my dirty bag (use four, one on each flap, so you don’t connect the gusseted bottom together). Then I strung lightweight paracord through the grommets.

  15. James Marcelia on April 2, 2018 at 7:29 pm

    Amazon says the Aquamira tablets are not available at your link. The other Chlorine Dioxide tablets I found were Katahdyn Micropur and it looks like they should be functionally the same. Any reason to look for Aquamira tabs over others and if so, where can I find them?

    • Andrew Skurka on April 2, 2018 at 7:54 pm

      Fixed the link, thanks.

      The Micropur tablets are chemically the same as those from Aquamira.

      • James Marcelia on April 2, 2018 at 8:19 pm

        Ok, thanks

  16. Dmitry on April 3, 2018 at 11:00 am

    Andrew, thanks for another great article. Are you familiar with the MIOX water purifiers? For example this one https://www.amazon.com/gp/product/B00LOGHPUM

    Best I can tell it produces a variation on chlorine (chloride?). It’s apparently the same technology that’s used by a lot of municipalities to purify tap water. I’d be interested to hear your thoughts. This reddit post https://www.reddit.com/r/CampingGear/comments/7g50ge/why_i_think_miox_should_be_in_everyones_kit/ was how I became interested in the tech.

    • Andrew Skurka on April 4, 2018 at 12:43 pm

      For whatever reason this category of purifier has not gained traction in the backpacking market. I think it’s largely the price — if it just produces chlorine dioxide, why spend $120 when you can spend $15 on Aquamira (albeit for only 30 gallons of it). Plus, the battery thing always makes me nervous.

      • dmitry on April 4, 2018 at 6:12 pm

        Fair enough. The price I see on amazon.com is $80, which is still significant.. I’m unavoidably attracted to gadgets that’s why I’m scrutinizing it so heavily. Aquamira is probably more practical for most use cases.

  17. Chris on April 5, 2018 at 4:41 pm

    If using the combination of chlorine dioxide and a Sawyer filter does the sequence of treatment matter for maximum effectiveness (chemically treat/filter or filter/chemically treat)? Also would swapping out chlorine dioxide for chlorine (NaDCC) offer the same ballpark of effectiveness? I’m aware that NaDCC is not as effective overall compared to chlorine dioxide (in particular against viruses) but I still have some NaDCC tablets that I am considering using in conjunction with a Sawyer filter for more questionable water sources.

    • Andrew Skurka on April 6, 2018 at 9:40 am

      The sequence matters a little bit. By filtering first, that will task the chemicals to working only on what’s left (e.g. viruses). Whereas if you use the chemicals first, they will have more work to do.

      However, I think the more important thing is that you give the chemicals enough time to do their job, whether that’s first or second. You wouldn’t want to drop in the chemicals and then immediately purify, because you might be filtering out some of those chemicals (like if you use a Sawyer Foam Filter or MSR Guardian).

  18. Dan W. on April 5, 2018 at 10:31 pm

    Sometimes bushcrafters get it right: https://www.youtube.com/watch?v=WS2SybqI8pI&t=7s

  19. Vic M on April 11, 2018 at 6:07 pm

    We carry a Steripen, a 3 liter Platypus Bigzip, and a Gatorade bottle. Most of the time we scoop 3 liters out of the stream & give it 1 zap with the Steripen. Yes, I know you are supposed to give it 3 zaps for 3 liters, but I’m guessing that 1 zap is good enough for most of the clear water we see. The Steripen fits in the mouth of the Gatorade bottle.
    We carry a Sawyer mini as backup, but we’ve never used it.
    Can’t argue with the other methods, but this has worked so far.

  20. Arne van Leuken on April 11, 2018 at 7:07 pm

    I swear by the combination of my MSR gravity filter, with water pretreated with Katadyn chlorine tablets. It’s lightweight, dependable, quick, and guarantees completely safe water.

  21. Doug K on April 13, 2018 at 2:35 pm

    steripen with aqua mira for backup..

    even on Boy Scout trips with 8-10 people, 2 steripens are adequate for drinking water on the trail. Carrying 2 in the group means one backs up the other, plus the aqua mira if needed.
    Evenings we’re cooking for a large group, and have Boy Scouts to carry extra fuel, so will boil water then.
    I don’t care for the filters in this situation since it is difficult to keep the inflow/outflow hoses separated and uncontaminated, with a pack of Scouts using them.

    I am hoping to do some long days running/flyfishing in the CO mountains this summer, trying to stay light will carry aqua mira and use Collin’s plan to purify as I go.

  22. Chris on April 16, 2018 at 1:23 pm

    Curious how you handle silty water on desert trips?

    • Andrew Skurka on April 19, 2018 at 9:52 am

      Let it sit for a while, ideally overnight, and then decant it into another bottle. If you do it smoothly, the silt will stay mostly in the bottom of the original container.

      Because silt will reduce the effectiveness of most purification products, it’s best to wait until after decanting the water before purifying it.

  23. Mark Roberts on June 17, 2018 at 12:39 pm

    I would urge you to check out the HydroBlu VersaFlow water purifier. Much lighter, cheaper, and faster than all Sawyers filters.
    I use mine set up as a gravity filter system, and it is much faster than either Sawyer product.
    It is very adaptable. Both ends are threaded to fit a typical UL plastic water bottle like you would find at a grocery available everywhere. You can use this for dirty bottle and clean bottle approach. I don’t use that. I use an UL 2-3 ltr dirty bag (w/ a large opening) that screws to the filter and an @ 3′ length of thin wall tubing to go to my clean water bottle/s. Soft wall bag/bottles are pretty useless when it comes to using as a dirty bottle trying to fill them.
    Alternatively, you can carry a dirty and clean section of tubing to connect to the filter and drink directly from a water source.

  24. Jud on June 26, 2018 at 10:45 pm

    Anyone have any experience with Purinize, a purifier product that claims to do everything, and with no toxic chlorine, only “sulfate mineral salts”? It is supposed to coagulate and flocculate the toxins from the water (over the course of an hour), which you then filter with a coffee filter to remove the sediment that has formed. The company basically claims it removes everything, including VOCS, heavy metals, viruses, bacteria, the works. Is it for real? Thanks everyone.

    • Amanda on May 30, 2019 at 4:24 pm

      This is really interesting, I wonder why this isn’t more popular?

  25. Brendan A on August 12, 2018 at 7:59 pm

    When you say you’ve had success using Aqua Mira with your guided group trips, are you waiting 15-30 min, or the full 4 hours?

    • Andrew Skurka on August 12, 2018 at 8:45 pm

      Usually 15-30. We recommend longer if not using a full dose, or if you can, ie let it sit overnight.

  26. Steve on February 17, 2019 at 3:47 pm

    To those of you using the SteriPEN, how do you sterilize the mouth of the water bottle?

    • Douglas K on July 17, 2019 at 9:54 am

      use the pen on the water bottle, then turn the bottle upside down with the cap loosely screwed on. This lets some of the clean water wash out over the mouth and the cap.
      So far no water-related illnesses, six years and about 3 trips a year with 6-8 Boy Scouts per trip..

  27. Mike G. on May 24, 2019 at 7:50 am

    Hi Andrew,

    I was wondering if you have encountered your premix not making as many batches as you put into it? I consistently find that I need to add at least one more dose (and usually two) of Aquamira than the number of liters I will be filtering as it doesn’t completely come out of my premix bottle.

    Perhaps this is just the bottle I’m using or maybe it’s just a side effect of the system. I also was wondering if over the course of a long trip, you would be concerned about this? Over time, I would guess that the small amount of premix left in the bottle would lose it’s potency. I suppose if it’s regularly being combined with new premix, it may be negligible.

    Just wanted to get your thoughts on this and see if you had any recommendations.

    • Andrew Skurka on May 24, 2019 at 5:28 pm

      If the number of premix drops is less than the number of A and B drops you put into the premix bottle, it’s because the drop size is different on the two types of bottles. Count how many drops go into the premix, count how many drops come out, and figure out an equivalent, e.g. 10 drops pre-mix = 14 drops total A & B.

      Premix will lose its potency. I only put about a day’s worth in the bottle, so I use it all up. I’ve heard it’s still good after 48-72 hours, but gets questionable thereafter.

  28. Jakub Badełek on June 13, 2019 at 1:31 am

    Andrew, thank you for the guide, it is very useful. However, I can see you focus on clearing water from biotic risks, but what about chemicals? it looks like one big disadvantage of chemical and UV purification is that it does not clean unwanted chemicals – only filters do, right?

    • Andrew Skurka on June 14, 2019 at 2:37 am

      Only certain filters extract chemicals. And there is an entirely different type of filter, Sawyer Select, that you might want to look at if chemicals are an issue.

      Where I normally backpack, chemicals are not a concern.

      • Bob S. on August 31, 2020 at 10:01 am

        I had a Sawyer Select S3. It was more trouble than it as worth. I scrapped the foam bottle and use the the screw-on filter from the select that can be backflushed as a prefilter for a GRAYL GeoPress. The GeoPress is fast and easy to use but it’s bulky as hell. I haven’t used the GRAYL Ultralight; I hear it is slightly harder to use than its bigger sibling.

  29. Chang Jung on November 5, 2019 at 7:58 am

    Not light as the chemical solution, but using a water rocket bottle (two Smartwater bottle spliced together) with the Sawyer Squeeze produces the easiest water filter system. The spliced two water bottle weighs less than a single bottle. Apparently, the bottom of the water bottle has more material & weighs more than the top portion of the bottle. You screw the filter to one end and open the flip cap on the other end, the water starts to flow into your clean bottle. There’s no squeezing or unscrewing filter to get more air into the dirty water bottle, etc. Search “4 gram Sawyer’s Squeeze gravity water filter system” on Youtube to see how this system works.

    I hope you share this tip with your readers so they can help other hikers.

  30. Thestraussdude on November 6, 2019 at 12:31 pm

    My complaint with the sawyer system is you aren’t supposed to let it freeze. I’m in cold environments too often for it to work well.

  31. Nike on February 7, 2020 at 1:46 pm

    Great post. I love Aquamira drops. Never had a bad experience over 1,000s of miles and love how easy it is to adjust treatment dose to any size water bottle or bladder. Light, simple, fast method for groups.

  32. Mike G. on March 4, 2020 at 9:28 am

    Hey Andrew,

    I see you mentioned that you switch to tablets below 15 degrees so Aquamira drops do not freeze. Good to know. If Aquamira does freeze in any state (Part A, Part B or premixed) does it reduce or eliminate its efficacy? Or is it just an issue of thawing it before it being usable?

    Also, do you have any issues with tablets not dissolving fully and if so, do you have a guess as to what causes it?


    • Andrew Skurka on March 4, 2020 at 9:33 am

      I doubt that it affects the efficacy, though I can’t say for sure. Maybe a chemist could chime in.

      I’ve rarely used the tablets (on my winter trips, there’s been no no running water, had to melt snow for it) so I haven’t asked as many questions about them.

  33. Craig on April 25, 2020 at 7:48 am

    Last summer we used the RapidPure inline water purifiers. It works as both a filter and a purifier. Flow rate was good and the manufacturer claims they are resistant to freezing damage. Highly recommend looking into them. Can be used inline, like a straw, and as a gravity-fed system.

    I was skeptical at first, but we had no issues.


  34. Ken on April 26, 2020 at 4:38 pm

    Looks promising.
    How frequently does the cartridge need replacement? (couldn’t find it on their website).
    What kind of set-up did you use? Looks like you need a wide mouth canteen or an inline set up for easy access while hiking?
    Avoiding the freezing problem is great.
    They say no pre-filtering is needed but the water they are dinking on their website already looks pure…they should show the straw used in the western desert with a small cow dropping filled puddle just discharged from a chemical plant LOL

  35. Craig on April 26, 2020 at 6:02 pm

    Well, they say that the purifier (Viruses) is good for 25 gallons, and the filtering function (bacteria, parasites) for 200 gallons. RapidPure claims that it also will deal with chemicals, heavy metals, and pesticides. I brought a spare purifier element in case of a clog. We had Micropur tablets as well which weren’t bad, either.

    We were on a 12 day trek in the backcountry of New Mexico at the BSA’s Philmont Scout Ranch. The last time that I was there, we used Polar Pure Iodine and frankly I hated the taste of the stuff. The kids would avoid drinking the water or would mix in drink mix to hide the taste. This time, we probably drank anywhere from 4-8 liters of water per day, so after the trek, I consider the filter ineffective for viruses and would replace it. Flow rate was very good – it did deteriorate a little bit over the course of the trip, but not enough to be a problem. Three of us used these purifiers and were very happy. The real beauty was to be able to fill the reservoir and drink without waiting for chemicals to do their thing.

    The setup that I had was a Platypus 2 liter big-zip with the Scout filter inserted in the drinking tube at a point where I could use a Velcro tie-wrap to attach the filter to the ladder on my pack’s shoulder strap. It allowed me to drink on-the-to, which was convenient and probably led me to drinking more water just because it was easily accessible.

    From what I understand, the RapidPure products will take a freeze once or twice without impacting the ability to purify, and multiple freezes and still operate as a filter

    We didn’t pre-filter. There was a lot of fine sediment in the water where we were and it could be a cloudy greyish or reddish color depending on where you were. We did take water one day from the only source around – a rather silty creek. It wasn’t until later that we discovered that cattle were drinking from and likely contaminating the water. Even after that, the water was clear downstream of the filter and good-tasting. Pretty close to the situation you’re describing – maybe without the chemical plant.

    I was worried the filter would clog or not be effective, but was pleasantly surprised. The price point isn’t bad either.

  36. Ken on April 26, 2020 at 6:06 pm

    thanks Craig.

  37. Yun on August 19, 2020 at 12:01 am

    May I know how you think of Cryptosporidium while using Aquamira? I’ve read the book where you say often you drink the purified water after adding Aquamira for 15 min yet that Cryptosporidium takes 4 hrs to be eliminated thoroughly. Is this because you’re willing to take the risk of Cryptosporidium?
    (I would like to choose between a filter and Aquamira, which the latter one is lighter and the bottles seems to be more easy to recycle after usage.)

    • Andrew Skurka on August 23, 2020 at 3:11 pm

      I have been using Aquamira for fifteen years, and we’ve been using it on my guided trips for ten (1,000+ clients). Never any issues. I know what the official advice is about crypto, but it seems to either be wrong or there is little crypto in the water we I backpack and run my trips.

  38. Yun on August 31, 2020 at 8:40 am

    Thanks for your reply!! I’ll definitely take this comment into consideration as well!

  39. Matt on October 10, 2022 at 4:10 pm

    While I wouldn’t necessarily recommend it for backpacking, pasteurizing water is all that is needed, a full boil is overkill. Depending on how efficient your boil is, pasteurizing generally uses around half to 2/3rds of the fuel compared to a full boil, and cuts your cooling time too.

    The main disadvantage of pasteurization compared to a full boil is that it can’t be visually verified. So if you want to go this route, there is a reusable device called a WAPI (water pasteurization indicator) that comes in around 5 grams. That is likely to be a break even on weight after pasteurizing 700-1000 mL instead of full boiling.

    The other (not as fuel efficient) way to pasteurize is to mix 3 parts of boiling water to 1 part untreated water, basically 25% off your fuel use with no extra devices needed, assuming you have the gear to measure water volumes.

    All in all, still an inconvenient and weight inefficient method, but “less bad” than boiling. For those interested, there’s a rather lengthy video on it: https://www.youtube.com/watch?v=rIMeq0c7rJM

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