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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