Aquamira: Why we like it, and how we use it

For about twenty years and almost exclusively I have used Aquamira ($15) to purify backcountry water sources. And it’s been the only purification method used by the guided trip program that I started in 2011 and that has over 1,000 alumni.

Last month two of these alumni emailed me separately, asking for a written explanation of our Aquamira methods. Alfredo wrote, “I am leading a group of ten new backpackers on a three-day trip in central Florida. I normally use a gravity filter but want to change to Aquamira after using it in the High Sierra.” And David wrote, “Please explain how your guides use Aquamira and the dropper bottles. I want to do the same on a trip next month to the Grand Canyon.”

TL;TR

The text in this post is slightly more nuanced and comprehensive, but this video will get you 90 percent of the way there, too:

Why treat

Water can be effectively treated by boiling it, treating it with chemicals (iodine, bleach, chlorine dioxide), filtering it, or subjecting it to UV light. All methods are designed to either kill, neutralize or extract pathogens (protozoa, bacteria, and viruses) that can infect a human with a waterborne illness. For a deeper dive on the pros and cons of these options, read this post.

In North America, we’re mostly concerned about having severe gastrointestinal distress, and giardia probably gets the most attention.

Why I like Aquamira

My recommended water purification method is Aquamira, a chemical treatment of chlorine dioxide. I prefer Aquamira for personal and guided trips because:

1. It works. I track injuries and illnesses, and Aquamira has a very good track record in our program. Clients or guides have rarely become ill during or after their trips, and these cases can often be attributed to likely human error (e.g. mixing up of purified and unpurified bottles).

2. It’s time efficient. In a 10-person group, at each water stop we treat at least ten liters of water. If this stop precedes a dry day or a dry camp, we could be looking at fifty liters (13 gallons)! With Aquamira, we can do this in just a few minutes. With filters or UV pens, each water stop would take substantially longer.

3. It has little aftertaste, unlike other chemical treatments like bleach or iodine.

4. It has few potential points of failure. Versus boiling, Aquamira is faster, better tasting, and less fuel consumptive. Unlike filters, Aquamira does not clog and require backflushing. Unlike UV pens, it does not rely on electronics, batteries, or fragile glass.

The advantages of Aquamira seem to hold in all of our operating areas, which in 2024 include southern Utah, Alaska, the High Sierra, Yellowstone, and the Appalachians.

I prefer the Aquamira drops over chlorine dioxide tablets like these from Potable Aqua ($18) because the drops are more flexible and more cost effective.

This 2-oz size (for both Part A and B) will treat about 60 gallons according to the manufacturer’s recommendations.

Manufacturer recommended process

To purify water, the manufacturer recommends these steps:

  1. Mix seven drops of Part A and seven drops of Part B into the provided mixing cap.
  2. Let this solution react for five minutes. It should turn bright yellow.
  3. Put the solution into one liter of water.
  4. Wait 15 minutes if you’re concerned about giardia, bacteria, or viruses. Wait up to four hours if you’re concerned about cryptosporidium.

Drawbacks in the recommended process

The manufacturer’s instructions will effectively purify your water, but it has drawbacks.

One issue is the physical bottles containing Parts A and B.

  • They are difficult to squeeze, probably because they are square-bottomed and because they’re made of overly rigid plastic. Cylindrical bottles are available now, too, but I’ve not used them.
  • The 1-ounce package (two ounces total of A and B) is way more than needed for normal trip lengths. For context, we carry this amount on a 7-day trip for a 10-person group.

A second issue is the 5-minute wait while Parts A and B react to each other. This time adds up over a day, and it’s disruptive to a hiking cadence. Also, the mixing cap is vulnerable to being stepped on or knocked over, or having debris land in it.

Finally, the recommended dose (fourteen drops total) may be appropriate for “worst case” water like a cow pond with poop floaties and a dead carcass, but it’s overkill for most water sources. When used on water taken from good-to-great sources, the water will have a noticeable swimming pool-like chlorine taste.

The square-bottomed bottles made of overly rigid plastic are very difficult to squeeze.

Disclaimer

Below I share how we use Aquamira. These practices are inconsistent with the manufacturer’s recommendations. So far they have worked well for us, but your mileage may vary. Follow this information at your own risk.

Our system: Bottles

We decant Parts A and B into these 10 ml dropper bottles from US Plastics, using an irrigation syringe. These bottles, which are light-proof and air-tight, are easier to squeeze and they’re more appropriately sized for smaller groups and trips of normal lengths.

To mark the bottles, I use this multi-pack of electrical tape:

  • Bottles with Part A are wrapped with apple red tape.
  • Bottles with Part B are wrapped with blueberry-colored tape.

By using a different dropper bottle, you run the risk of having bottles with unequal drop sizes, i.e. Seven drops of A and B actually translate to 10 drops out of your dropper bottles. It’s important to test the relative drop size and to adjust accordingly.

Our smaller and softer dropper bottles are marked with electrical tape: apple red for Part A, blueberry for Part B, and yellow for the premix.

Our system: Premix (no wait time!)

At the first water source or in the morning over breakfast, we premix Parts A and B into a third dropper bottle. If we use another 10 ml bottle, we wrap it in yellow tape. Soloists may want to use smaller premix container, like this 6 ml bottle.

Important: If you are making the premix, ignore anyone who tries to talk with you. If you want to talk to the person making the premix, wait until they are completely done.

A 10 ml bottle will hold about 75 drops of both Part A and B, for a total of 150 drops. In our program, this is enough to purify about 20 liters of water.

By making the Aquamira beforehand, we avoid the 5-minute wait time that’s part of the manufacturer’s recommended process. In addition, our capped premix bottle is more secure than the provided mixing cup.

The effectiveness of premix over time is not officially established. I’ve heard reports of it being okay for several days, but I encourage my guide team to cook a new batch of Aquamira each morning. This daily routine seems more reliable than trying to recall if the premix is from, say, Tuesday morning or Wednesday evening.

Our solution: Dosage and dwell times

The manufacturer recommends a mixture of seven drops of both Part A and B (fourteen drops total) per one liter of water, and before drinking waiting at least fifteen minutes (or four hours if there’s a risk of cryptosporidium).

Cryptosporidium

We never intentionally wait four hours, even in a location like southern Utah where there’s little water and almost no high quality water. I only have one record of a client testing positive for crypto, six years ago in Rocky Mountain National Park. This means that one of two things:

  1. Cryptosporidium is not common where we operate, or
  2. Aquamira more rapidly purifies water contaminated with cryptosporidium than stated by the manufacturer.

Dosing

Instead of the recommended fourteen drops (seven of both Part A and B), we often use just half that amount — that is, seven drops of premix per one liter of water, if we want it drink-ready in fifteen minutes. If the water is high quality, I may use less, like four drops of the premix; if the water has an unpleasant odor or color, I may use more, like ten drops.

Water with this smaller dose has much less chlorine taste. And it still must be effective because we’ve been doing this for a long time with only very rare incidents.

Dwelling

If the water is not needed in fifteen minutes, the dosing ratio can be reduced even further. For example, I will treat a 2.4-liter Platybottle with only seven drops of premix, then give it hours to do its thing, like overnight or between breakfast and lunch.

Ownership

With Aquamira and most other water purification methods, too, it can be difficult to retroactively determine bottles that have (or have not) been purified. Aquamira may give off a bleachy odor and sometimes will off-gas, but neither observation is reliable.

We put the onus on each group member to own their water purification, specifically by knowing:

  • Which of their bottles has been purified (or not), and
  • When their bottles will be safe to drink.

This system of ownership works well until a “water party” offers to fill up and purify bottles for other members in the group. In this case, it’s imperative that the water party have a good system for tracking bottles that have (or have not) been purified. To help distribute bottles to their correct owners afterwards, it’s helpful to mark all bottles, like with that leftover electrical tape.

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Posted in , , on March 1, 2024
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49 Comments

  1. Yves on March 4, 2024 at 9:58 pm

    That’s not the method the GOAT Bear Grylls used when taking Natalie Portman on the expedition.

  2. Tiago Costa on March 7, 2024 at 4:25 am

    I didn’t quite understood why don’t you like the tablets?

    • Andrew Skurka on March 7, 2024 at 8:43 am

      1. Not as flexible. The tablet is a full dose, even if you don’t want it, which we often don’t, like if the water quality is good-to-great (in that case, a half-dose has proven to be fine) or if the water can purify for a long period of time before it’s needed (e.g. overnight, between breakfast and lunch).

      2. Not as economical. A 30-pack of tablets that is designed to treat 30 liters of water runs $19. A 1-oz package of drops that will treat 30 GALLONS of water runs for $15. So drops are 1/4 the cost, and that’s before half-dosing water that doesn’t need full-dosing.

  3. James on March 12, 2024 at 6:08 pm

    I loved Aquamira until we used it with similar dilutions as recommended for a 5 month thru hike. In hindsight we were likely overly cautious, but not wanting to jeopardize the goal we could not tolerate more risk from water borne illness. Further, building the habit loop kept us safe through consistency. At the end of the hike we had indicators that we may have had a weakened gut biome which was surprising consider that we ascribed to a relatively strict high nutrient density, low inflammation, diet during the hike.

    Assuming comparable safety from all purification technologies acknowledged in this article, I’m curious what Katie’s thoughts are on the nutrition/gut implications of prolonged use of this product (or other chloride options) when compared to non-chemical alternatives?

    • Andrew Skurka on March 13, 2024 at 10:36 am

      I’ll forward this to Katie, to see if she has something to add. She’s traveling today, it maybe a few days until she responds.

      Some of my thoughts:

      1. I also used Aquamira for very long thru-hikes, without observing the issues that you did. But this is certainly not definitive proof of anything, and your story is not either. I did have a client last year report gut issues after our trip that his doctor speculated was due to Aquamira, but no one else on the trip reported anything similar and the doctor had no evidence to support his theory.

      2. About five percent of US water treatment facilities use chlorine dioxide. If it was consistently weakening gut biomes, you’d think they’d use something else. However, I don’t know the relative ratio of this chemical in municipal-treated water versus Aquamira. I would not be surprised if Aquamira was recommending a higher dose — there probably is some economies of scale when purifying millions of gallons of water.

    • Katie Gerber on March 15, 2024 at 5:51 pm

      When I first started long distance hiking, I avoided chemical treatment due to concerns of the effect it may have on my microbiome. I didn’t have any specific research to back this up, but knowing that chlorine dioxide is a strong antifungal, antibacterial, and antiviral agent (which is what makes it an effective water treatment method), it seemed likely that it could affect the gut microbiota, at least subtly.

      As I did more hiking in the desert, I started using Aquamira more regularly. I haven’t noticed any overt effects. That said, my gut health never seems as good during hiking season as it does during the ‘off season’, which could be due to the chlorine dioxide, eating more dehydrated food, not sleeping as soundly, and heavy exertion, or some combination of those.

      A possible reason that some people experience issues with chemical treatment while others don’t is that everyone has a slightly different microbiome and some are more sensitive than others.

      As far as I know there’s no research that’s been specifically done on Aquamira and it’s effects on the microbiome, but for people who suspect they may be particularly sensitive to it, I think sticking with non-chemical options is a good alternative, especially for extended trips. Focusing on rebuilding the microbiome post-hike could be an effective strategy as well.

    • Thomas on March 16, 2024 at 9:31 pm

      Chemist here, so there may be some professional bias here, even if I do not think so (That’s how bias works, I think 😉 ). It seems most unlikely, to me at any rate, that any active chlorine dioxide will survive long enough to reach your gut. The stuff is so reactive and, at the recommended dose, present in such small amounts that it will long have been quenched by oxidizable stuff in your stomach that it will be finished by the time it would reach your gut.

      I attribute any changes in my digestion during trough hikes to the radical change in my diet from green to beige stuff (my version of Andrew’s meals).

      Being a scientist, I have an idea for an experiment: use Aquamira at home while eating what you usually eat and see whether there is a change in your microbiome (however you determine that) :^).

      Lastly, if the experiment is not your deal, there is an easy way to disarm all chlorine-based disinfectants in the amounts used for water purification: add a small tablet of vitamin C! 100 mg is plenty.

      • Andrew Skurka on March 17, 2024 at 9:30 am

        I’m glad you mentioned the change in diet, because I have some personal A/B testing observations from the past year.

        Up until about six months ago, I was running about 50 miles per week, which was on the low end of the normal range (60-80) that I had maintained for several consecutive years.
        GI was very active. Almost as soon as my feet hit the floor in the morning, I needed to go to the bathroom. Loose stools, always.
        On backpacking trips, I would experience no change.
        I attribute this experience to: lots of exercise, lots of water, lots of food.

        Six months ago I essentially stopped running, except for on some weekends, when I go out for a casual half-hour.
        GI has slowed down remarkably, and it takes a while in the morning for things to get moving in the morning. The process involves more effort, and the stools are notably more solid.
        I attribute this experience to: less exercise, less water, less food.

        My point: The GI change that many experience when they go backpacking is probably a function of exercise and water/food intake, not Aquamira.

      • Drew on March 22, 2024 at 5:06 pm

        Hello, since your credentials are a good fit for my question, I am replying to you. Is it safe to assume that the “effective dose” of aqua mira (chlorine dioxide?) is proportional to the amount of bacteria present in the water? Many claims in this article seem to hinge on this assumption, so I would like to know if there is some mechanism of action that would, at least in theory, allow for a proportional relationship.

        Assuming there is such a mechanism, then I would also assume that the same principle would apply to dwell time.

        There must be enough product (sodium chloride?) to react with all bacteria present, and assuming these reactions are time restricted, there must also be enough time for the reactions to take place.

        Are minimum effective dose and minimum effective dwell independent variables?

        • Thomas on March 22, 2024 at 9:10 pm

          The vessel with pre-mixed Aquamira does not know anything about the water, obviously, so the question as phrased or as I understand it, does not make sense.

          I vary the amount of premixed Aquamira I use as a function of the presumed quality of the source water, as Andrew does (see his statement about 7 drops vs. 14 drops/liter).

          In general prefiltering and removing solids as much as possible is an easy way to improve the source water before treatment as is the proper selection of where you collect your source water. Life is pretty hard for a microbe in water that does not contain particles, they have a much easier time when attached to a surface. So if you remove particles, you also remove a significant fraction of the bacteria in the source water. Moreover, any non-living material organic material will react with the reactive oxygen species that is generated when Aquamira solutions A and B are mixed. Therefore, if you remove the crud, more active reagent is available to react with the microbes.

          The prefilter could be a bandana, I carry a sump pump sock when hiking in Utah. With really turbid source water (think cow tanks in Arizona) I also remove dirt particles by adding a few drops of “alum” solution, which coagulates suspended particles that make it through the filter into larger particles that settle easily (for an image see [email protected] “Treatment of turbid water”).

          Lastly, dwell time. The colder your water, the longer the reaction will take. The temperature coefficient is 2, meaning for every 10 degrees Celsius/Kelvin (for the pedants) decrease in temperature the reaction will take twice as long, i.e. water that has frozen over night will probably require a reaction time of >> 30 min.

          The components by themselves, or a premix, are not sensitive to freezing. Once you mix them, the reaction to create the reactive oxygen species is again subject to the temperature coefficient. It is obviously easy to hold the little vessel in your hand and get around that.

          • Drew on March 25, 2024 at 1:47 pm

            Thank you for your reply. As I outline in my response to the article in a comment below, and as you point out, the amount of organic microbes that can be neutralized is proportional to the amount of “reactive oxygen species” generated in the pre-mix. This was the question I was asking. Additionally, the amount of organic microbes that can be neutralized is proportional to the dwell time, the longer the dwell time the more microbes are neutralized (assuming the initial concentration of Chlorine Dioxide is sufficient). Additionally, the larger microbes like crypto require substantially more dwell time to reach the required reduction for a given initial concentration of Chlorine Dioxide. Dwell times are only effective if there is ample Chlorine Dioxide to react with the microbes present. If, for example, you start out with an insufficient amount of Chlorine Dioxide for the level of microbes present in the water (due to voluntarily reducing dosage), then you could have a dwell time of 8 hours but still not kill all the microbes. The difficult part seems to be in determining the exact amounts and “safety factors” at play in these reactions.



  4. Ellie on March 22, 2024 at 3:25 pm

    I’m a fan and have used it over thousands of miles with no ill effects.

  5. Phil Johnson on March 22, 2024 at 4:07 pm

    I remember Mike Clelland mentioning it in his book but had always used filters until I did a Skurka trip to the Olympics last fall. After that trip, I’ve switched to Aquamira and even got the little dropper bottles too. Was Mike the originator or this method?

    • Ramesh on June 8, 2024 at 10:41 pm

      I remember watching his videos which dates back to 11 years, I dont know for sure who is the originator but Mike Clelland certainly had good UL tips back then itself.

  6. Randy Lee on March 22, 2024 at 4:08 pm

    Isn’t there a number (3, 5, other?) in the sentence on dosing where you indicate you might use fewer drops for water from relatively cleaner sources? Specifically, “I may use less, like [missing number?] of the premix;…”

    One hazard that you didn’t address is that of invisible destruction of Katadyn BeFree (which I use and like for weight & convenience) and Sawyer Squeeze water filters from freezing. Do you know how Aqua Mira, including the premix, stands up to freezing temperatures, as often can happen unexpectedly (and easily go undetected) overnight?

    Excellent article, thanks for sharing the specific experience-driven judgment calls you’ve made on the topic.

  7. Randy Lee on March 22, 2024 at 4:08 pm

    Isn’t there a number (3, 5, other?) in the sentence on dosing where you indicate you might use fewer drops for water from relatively cleaner sources? Specifically, “I may use less, like [missing number?] of the premix;…”

    One hazard that you didn’t address is that of invisible destruction of Katadyn BeFree (which I use and like for weight & convenience) and Sawyer Squeeze water filters from freezing. Do you know how Aqua Mira, including the premix, stands up to freezing temperatures, as often can happen unexpectedly (and easily go undetected) overnight?

    Excellent article, thanks for sharing the specific experience-driven judgment calls you’ve made on the topic.

  8. Randy on March 22, 2024 at 7:34 pm

    Andrew,
    Only used the Aquamira once or twice, carry it as backup. Have used the squeeze the Be Free and a Be Free gravity for years.
    But would like to use the Aquamira in place of the filter, so was thinking using in camp for the next day. My question is do you use a dirty bag, put the chemical in let it do its thing and pour into your drinking bottle or just dunk your drinking bottle in and drop your chemical in to work over night? I have read cleaning the threads and top of the bottle with chemical is a good idea.
    Your articles are Great and very helpful over the years,
    Thank you
    Randy

    • Darren on March 23, 2024 at 8:24 am

      Not trying to reply to Randy, but to the articled in general. I learned a trick from a NOLS instructor whose team has been using grapefruit seed extract for all their trips. I add about 8 tiny drops from tiny bottles per liter of water. The sterilization properties of GSE are many. It is much cheaper than any chemical treatment and totally natural. There can be a slight citric acid taste that is not a problem.

    • Andrew Skurka on March 27, 2024 at 8:45 am

      If you are concerned about a very tiny amount of water from the threads getting you ill, I’d probably first consider whether I could get water elsewhere. I’d have that concern if I was getting water from the middle of a cow pie, but most water doesn’t have that level of contamination.

      As a precaution, regardless of the water quality, you could squeeze a bottle full of purified water with the cap partially threaded, so that purified water runs through the threads and expels any non-purified water.

  9. Barry Blanchette on March 23, 2024 at 9:46 am

    Love this system. I’ve have gone back and forth with a variety of filtering methods and never really settled on one I was 100% behind. Had a few follow up questions on this process:

    1) I had read that Aqua Mira can freeze but in prior comments someone suggested it does not. Is it a lower freezing point than water so it is not a concern? Do you do anything to mitigate this risk (i.e. sleeping with it, etc.) or have you not had that issue? You obviously travel in very cold climates on some of your trips. Curious what you do with the bottles.

    Skurka reply: If you’re concerned about it freezing, you can keep it in a jacket pocket close to your body, or at least insulated deep in your pack if it’s not a deep cold. Although, if it’s deep cold, you’re probably not purifying the water anyway because you’ll be melting snow for water.

    2) Curious how you filter particles and debris from initial water collection. There are a variety of products out there but they are generally bulky and tedious. I assume you have an ultralight/minimalist way of doing this too. Even a reliable, good flowing source can have algae particles, sand, bits of leaves and other debris which I assume could compromise the effectiveness of the treatment.

    Skurka reply: With where I backpack most regularly, sediment is the biggest issue, specifically in southern Utah. The solution here is to just let the water sit for a while in a bottle, to let the silt settle, and then decant the good water into another bottle. This would be tedious if you were doing it all the time, but there’s not a lot of water in this location so you’re usually just filling up a few times per day. You’d be amazed at how much silt will settle in just 10 minutes. As far as the other things you mentioned, try a metal coffee filter or bandana, or just chew while you’re gulping.

    3) You stressed not confusing “dirty” and “clean” water bottles. I assume you mean during actual water collection? Why would you be carrying dirty water? Wouldn’t you treat it all when it is collected so everything you have is ready for use? Probably overanalyzed your YouTube video but if I’m missing a key point please clarify.

    Skurka reply: Don’t confuse dirty and clean as they are being purified. For example, the process might look something like this: (1) collect all the water and put all the bottles in one pile, (2) as you treat with them with Aquamira, create a new distinct pile. If you were to run out of premix during this, then you’d have to create a new system, like (1) George is carrying back to the group all the purified bottles, and (2) Sally has all the bottles that still need treatment.

    Great article.

  10. Will Evans on March 23, 2024 at 10:33 am

    Is there any concern over Aquamira freezing (aside from breaking the bottle)? I’m a sawyer squeeze user but thinking of switching.

    Do you prefilter when getting water from dirtier sources, if so, how?

    • Andrew Skurka on March 23, 2024 at 3:17 pm

      I’ve used Aquamira on winter trips when I could sometimes find running water and when I sometimes had to melt snow, and the Aquamira worked as expected.

      I don’t normally prefilter my water, but my tolerance is pretty high. Some options: metal coffee filter or bandana, alum, or let it sit overnight and decant the better water off the top (works great with silty water)

      • Will Evans on March 23, 2024 at 3:57 pm

        I may not have phrased my comment clearly. Do you have keep the aquamira bottles from freezing. For example, do you sleep with them in your sleeping bag like you would a Sawyer on cold nights?

        • Andrew Skurka on March 24, 2024 at 9:41 am

          I never have.

  11. Kelly C on March 24, 2024 at 9:43 am

    I’ve wondered if it were possible to mix the A and B beforehand so it would be ready to use rather than mixing drops and waiting at each water source. Apparently the answer is “yes.” Glad I came across this!

  12. David S on March 24, 2024 at 10:44 am

    I am hoping someone can address Randy’s question. When a bottle is submerged to scoop up water and then you chemically treat the water inside the bottle, the threads on the outside of the bottle (used to screw on the cap) remain contaminated by untreated water. The threads will later touch your mouth. I realize that this is only a tiny dose of untreated water and that the risk of disease is dose-related, but I would still like to learn about any techniques people might use to reduce this admittedly small risk.

    • Nate on July 21, 2024 at 10:58 am

      I never dip my bottles unless absolutely necessary. I filter/pump into, or pour filtered water directly into my bottles taking as much care as possible to keep the rim, threads, cover and bottle dry. Once I have put the aquamira mix into the bottle, I shake it to mix it, then loosen the threads, tip and rotate to allow mixed water to coat the threads and rim, then tighten and wait the 15 minutes. I am a huge fan of aquamira.

  13. Drew on March 25, 2024 at 11:09 am

    This is a must watch video for anyone seeking cold, hard, scientific information about Aqua Mira and other Chlorine Dioxide products:

    https://www.youtube.com/watch?v=_RBavPWLOKg&t=1748s

    Key takeaways:

    1) There is a proportional relationship between amount of Chlorine Dioxide and disinfecting power.

    2) There is a proportional relationship between dwell time and disinfecting power.

    3) A concentration of 4ppm Chlorine Dioxide per 1L water is required for the listed dwell times to be effective.

    4) Premixing the solution (in the manner described in this article) WILL result in a decrease in the total amount of Chlorine Dioxide present. How much of a decrease is unknown but could be calculated with enough information.

    5) After the Chlorine Dioxide solution is added to the water to treat, it must be kept away from sunlight (opaque bottles or putting clear bottles inside pack).

    6) Reducing dosage, dwell time, or pre-mixing will result in a decrease in the amount of Chlorine Dioxide and thus disinfecting power. Doing all three at the same time will drastically reduce disinfecting power (to what degree is unknown).

    7) Temperature of the final solution (Chlorine Dioxide solution + water to treat) affects the required dwell time. Colder water requires longer dwell time than warm water.

    8) No information on what happens when either part A, part B, or the pre-mix solution freeze, or even if they are able to freeze. Not all chemicals are the same after a freeze thaw cycle, so we would need confirmation from the manufacturer that freezing isn’t detrimental.

    Final thoughts: it is nearly impossible to know how the required dosage and dwell time for a given source of water. Put another way, it is nearly impossible to know how “pure” a given source of water is. The manufacturer is supplying a formula for dosage and dwell time that meets the EPA requirement, which is absolutely a worst case level of contamination. Any deviation from this worst case formula incurs risk of the water not being fully decontaminated.

    If you are to accept this risk, then I think the information in this article is useful. If you want to be absolutely sure that your water is safe, then you’re going to have to deal with the 5 minute premix and the 4 hour wait time (with no sun exposure during those 4 hours!), AND deal with the funky taste.

    All outdoor activities have some risk. Each individual will have to decide for themselves if the risk to reward ratio for this method of water treatment is right for them.

    One thing I would like to find out, is what the reduction rate in the total amount of Chlorine Dioxide is during the mixing reaction. Andrew recommending to pre-mix new solution each morning means that probably worst case the pre-mix is being used 10-12 hours after mixing. I would like to know what the final concentration of Chlorine Dioxide would be in this scenario. If I find information relating to this, I will comment again.

    • Drew on March 25, 2024 at 12:51 pm

      On the question of the mixing reaction (part A and part B) I have come to understand the following: Part A is sodium chlorite buffered with some alkaline to make it “stabilized”. When mixed with part B phosphoric acid, a chemical reaction begins, which produces aqueous Chlorine Dioxide at a certain rate determined by a first order rate law. The manufacturer describes the 5 minute point to be the time at which production of Chlorine Dioxide is at the maximum. After this time, the rate of production begins to decrease, causing the total amount of Chlorine Dioxide present to decrease, because there is a constant loss due to alkaline decomposition of whatever Chlorine Dioxide is present.

      Key takeaway: when left to sit, total amount of Chlorine Dioxide reduces due to alkaline decomposition of Chlorine Dioxide into chlorate, chlorite, chloride and oxygen.

      The rate of decomposition can be calculated with enough information (specific chemical formulas and concentrations for Part A and Part B), but I dont think that information is publicly available. So, unfortunately, only the manufacturer can answer this question, which they are highly unlikely to do.

      The Chlorine Dioxide tablets do not suffer from this unquantifiable loss, they are lighter (both in terms of weight per given quantity of water treated, and because they do not require carrying plastic bottles). Downside is they are more expensive per quantity of water treated, but only by 4x. And for quantities of water smaller than 1L, they cannot be diluted easily. In the context of a guided trip where you are treating 10L of water separated into 10 separate 1L bottles, reducing dosage would be difficult.

      I’m all for reducing dosage and dwell time based on the assumed contamination level of the water. And really only the drops allow you to reduce dosage effectively.

      I worry though that the pre-mixing of part a and part b could result in NO active ingredient (Chlorine Dioxide) being present when added to dirty water, depending on how long it has been since the initial reaction.

      I will continue to try to find information on this topic.

      • Drew on March 25, 2024 at 2:16 pm

        I have found low range (0 to 100 ppm) test strips for Chlorine Dioxide. I will test the INITIAL concentration of aqua mira in 1L of water using the following methods:

        0) pure water (reverse osmosis) with nothing else (baseline)
        1) tablet form after tablet has dissolved (control should read 4ppm)
        2) drop form according to manufacturer instructions (should read 4ppm as well)
        3) drop form according to Andrews instructions (full strength, 5 minute mixing time)
        4) drop form according to Andrews instructions (half strength, 5 minute mixing time)
        5) drop form according to Andrews instructions (full strength, 30 minute mixing time)
        6) drop form according to Andrews instructions (full strength, 1 hour mixing time)
        7) drop form according to Andrews instructions (full strength, 4 hour mixing time)

        Tests 6 and 7 will only be conducted if there is measurable PPM of Chlorine Dioxide for test 5. I will report back with my findings. Empirical data will have to suffice since I dont think we’ll ever find out the exact chemical compositions and strengths from the manufacturer.

        • David Schmidt on April 6, 2024 at 11:29 pm

          Drew, I am very interested in hearing the results of your test. Thank you for doing it.

        • Drew on April 15, 2024 at 10:52 am

          I completed the testing. The test strips turn a varying shade of blue, and the bottle has a color scale. I will list the concentration, and when the color on the test strip is between two reference colors, I will list the range with my best guess at the actual ppm in parenthesis.

          I also changed some of the proposed tests based on the time I had available and the results of the first tests.

          Results:
          0) 0 pmm
          1) 10 – 25 ppm (20 ppm)
          2) 10 ppm
          3) not tested
          4) not tested
          5) not tested
          6) 5 ppm
          7) 2 – 5 ppm (4ppm)

          8) drop form according to Andrew’s instructions (full strength, 6 hour mixing time) – 0.5 – 2 ppm (1.5 ppm)

          9) drop form according to Andrew’s instructions (full strength, 10 hour mixing time) – 0.5 – 2 ppm (1 ppm)

          10) drop form according to Andrew’s instructions (half strength, 1 hour mixing time) – 2 – 5 ppm (4 ppm)

          11) drop form according to Andrew’s instructions (half strength, 4 hour mixing time) – 0.5 – 2 ppm (1 ppm)

          Conclusions:

          Premixing results in adequate (4ppm) concentration of Chlorine Dioxide if used within 4 hours at full strength (7 drops each per 1L water), or within 1 hour at half strength (4 drops each per 1L water).

          With further testing and more precise measurement of Chlorine Dioxide concentration, it should be possible to create a chart of required drops of premix for full 4ppm concentration for each hour after initial mixing. You’ll have to infer a “dosing schedule” from my data, as I do not wish to conduct any further testing.

          Waiting longer than these times results in a initial concentration of less than the required amount for the log removal rates necessary to meet the EPA standard.

          At the reduced initial concentrations, the solution may still be adequate to treat the water, or it may not. Since there is no possible way to test the contamination level of the water, it is a game of probability whether you 1) drink water that is not adequately treated and 2) whether you get sick from that. See the excellent series on this topic from the YouTube channel GearSkeptic that I linked in my first comment.

          Not everyone who receives the amount of contaminated water required to get sick will be symptomatic. This causes an abundance of false negatives, which creates a sort of false confidence that the methods/concentrations a person chooses to use are effective (assuming they are using the metric of people not getting sick as a measure of success).

          • Jason McGrath on April 15, 2024 at 5:30 pm

            Drew, did you keep the mix in an airtight and opaque container?



          • Drew on April 15, 2024 at 5:38 pm

            I cannot reply directly do Jason McGrath, perhaps because the reply depth is too great.

            Yes I used an airtight opaque container. I also put that container under an opaque cover to be 100% sure no light was reaching it. The water bottles with the aqua mira mixed solution were also covered under this opaque cover.



          • Jason McGrath on April 15, 2024 at 5:50 pm

            Thanks Drew.



          • Jason McGrath on April 18, 2024 at 5:09 pm

            Hi Drew, I thought of another question about your test. Did you use the Aquamira bottles to measure drops? Or did you use aftermarket bottle droppers like the ones Andrew linked? I’m asking because I’ve seen estimates that the aftermarket droppers have significantly smaller drop sizes (Andrew did mention this even though it appears he doesn’t compensate in practice).



          • Drew on April 19, 2024 at 10:38 am

            Jason, I used the aquamira bottles to measure the drops. I only pre-mixed the exact amount required for each test. So I added 7 (or 4) drops from each container to an opaque test tube, capped it, put it under the opaque container for the desired pre-mix time, then opened it up and poured it all into the clean water. Then I put the water under the opaque container and waited the 15 minute dwell period per the mfg recommendation, then took it out of the opaque container to measure the concentration of Chlorine Dioxide.



          • MR on August 1, 2024 at 12:41 pm

            Thanks so much for all the information you relayerd, and for the testing you did!



          • Doug on September 14, 2024 at 11:22 am

            Very interesting and well planned testing. Thanks!



  14. Craig Smith on March 28, 2024 at 10:09 pm

    I have an interesting history with chlorine dioxide that began 15 years ago from a GI parasite infection I picked up from a salad bar in Jackson Hole. I could not shake the parasite infection for several months and it was becoming very debilitating. I crossed paths with a sports doctor from South Africa who recommended using chlorine dioxide (CLO2) treatments to cure the parasite infection. Long story short: after 3 weeks of structured treatments taking CLO2 directly the infection in my GI tract was gone. It was years later that I “discovered” how to use CLO2 to purify water (haha!) – and is now my #1 go to for water purification. Another interesting FYI: a worldwide organization of 4,000 + medical professionals exists researching, conferencing, prescribing, and publishing the use of CLO2 (www.comusav.com) – unfortunately mostly in Spanish. Here is a good comprehensive online source from a US medical practitioner if you are interested: http://www.theuniversalantidote.com. Hope this is useful.

  15. Jason McGrath on April 4, 2024 at 1:02 pm

    Andrew, thank you for sharing this!

  16. Michael Volk on April 12, 2024 at 8:09 am

    When you start a hike, pack as much water as you think you need and are willing to carry. If you empty your first bottle, and come upon a water source, estimate if you have enough remaining water to finish your hike. If no, fill your empty bottle from the water source, and add a half hour tablet. I would prefer the foil wrapped so you don’t have to carry a bottle around. Then, if at any point you run out of water, and feel you are compromising yourself by not drinking and waiting till the next potable source, drink the treated water. At your next potable (or safer) water source, dump the remaining treated water and clean out your bottles and refill.

  17. Michael Volk on April 12, 2024 at 8:11 am

    It doesn’t make any sense to me to try to be economical with something so important as water treatment, which could cost you your life. Pick the option that is most effective/most convenient without any regard as to the cost.

  18. Doug on September 14, 2024 at 10:49 am

    I’ve used AquaMira and many other treatment methods for decades with few problems. And chlorine dioxide is commonly used in municipal water treatment.
    BUT AquaMira is NOT tested or licensed for making unsafe raw water safe to drink. It’s only approved to prevent slime buildup in containers of already safe water, like in an RV or boat; NOT for treating surface water. The manufacturer’s wording is very precise and never makes a claim otherwise. I think it does work but there is little evidence to support that this portable point of use method does what the industrial systems do. Hard to believe but look it up. The European silver based treatments are also limited to water storage.
    The tablet “chlorine dioxide” products contain sodium chlorite to make chorine dioxide, but also contain a dose of sodium dichloroisocyanurate aka NaDCC, the bleach equivalent active ingredient in Aquatabs etc. NaDCC IS approved for surface water but misses crypto and tastes bleachy. So you can microfilter cysts out, then treat with NaDCC or with ‘chlorine dioxide’ tablets. Or boil the water, or use an ultrafilter, or if it’s super clear and not icy, and you trust your equipment, use a UV pen.
    “Mixed oxidant” makers (batteries and salt, like Miox or H2gO) produce a mix of chlorine dioxide with other chlorine compounds that work together to act like the ‘chlorine dioxide’ tablets but also taste bleachy. They seem to be approved too, to either WHO (misses crypto) or US military (twice as concentrated) standards.
    Water mixed with chlorine dioxide has to be kept in the dark during treatment, so put a cover on that Smartwater or Nalgene. And +1 to the comment above about adding a pinch of vitamin C (aka PA-Plus) after treatment to kill the chlorine (or iodine) taste. With chemical methods, half the dose needs twice the time, or vice versa, to achieve the same results.

    Look at https://journals.sagepub.com/doi/10.1177/10806032231218722 for a (very) complete summary of wilderness water treatment science.

    • Doug on September 14, 2024 at 11:08 am

      It is worth noting, too, that a lot of backwoods water products aren’t officially approved or tested to consistent standards. Look at MSR’s blog post about this at https://www.msrgear.com/blog/water-101-decoding-water-filter-testing-claims/ for some information about filters. But chemical treatments are “pesticides” that must be approved by the EPA for specific purposes (and “it is a violation of Federal law to use this product in a manner inconsistent with its labeling…” etc. AquaMira is EPA Reg No 71766-1 – link just shows you text of the approved label.

  19. Jason McGrath on September 14, 2024 at 11:26 am

    I used Aquamira all summer using Andrew’s recommendations. Except I adjusted the dose to account for the 3rd party bottle’s drop size. I really liked how much more convenient it was. I was more conscious of where I was getting my water from, however.

  20. Phil Farrell on October 15, 2024 at 11:59 pm

    Hi Andrew,

    Very interesting article. When talking about dosing, you state:
    “Water with this smaller dose has much less chlorine taste. And it still must be effective because we’ve been doing this for a long time with only very rare incidents.”

    I’ve been drinking water in the High Sierra with no treatment at all for 54 years of backpacking with NO incidents of illness. Does that prove that natural waters in the High Sierra are free from disease causing organisms? No. Maybe I’m just lucky. Maybe my gut fights off organisms better. Maybe I’m very careful about just which water sources I use. There are also many “maybes” that affect your statement of “very rare incidents”, so your experience is not really proof that the water is disinfected.

    • Andrew Skurka on November 4, 2024 at 8:30 am

      My statement wouldn’t pass the scrutiny of an editor in a science journal, for sure.

      But I’ll stand by what I said, with a little bit more context. We’ve been using half-doses in water sources that are most definitely contaminated, like creeks with beaver activity, lakes with high-use campsites all around the shoreline, small potholes that smell like cow shit and that have hoof prints all around them, etc.

      In the High Sierra, I almost never purify my water because the water is generally excellent. If we were only operating there, I’d be less confident in my anecdotal assessment of the effectiveness of Aqua Mira in a half-dose scenario. But that’s not what is happening here. Plus, we’re talking about thousands of clients in these areas ingesting thousands of gallons of water. If it weren’t working, we’d have more consistent cases of giardia in our groups.

  21. Dow on October 26, 2024 at 7:08 pm

    Aquamira is very tempting to me. However, one of my water strategies in low-water environments is “camel-ing up,” i.e. chugging water at a water source in order to carry more at less of a on-the-back cost. Do you wish you could do this with aquamira Andrew? Another solution?

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