Introduction
The purpose of this article is to present three ultralight water treatment options for backpacking. We chose these three for their diversity and efficacy, and they include a chemical method, a physical method, and an electro-ultraviolet method. We included a video to show each of the three technologies used in the field.
Based on the results of my most recent analysis of internet keyword searches, paid advertising buys from manufacturers, and interviews with industry contacts who work for outdoor gear distributors, the most popular water treatment option among backpackers is still the pump-style water filter. Two of the lightest examples include the Katadyn Hiker (11 oz) and the MSR Hyperflow (8 oz).
The problem with pump style water filters is that they’re relatively heavy, they’re sort of difficult to clean, and they clog easily. And of course, it requires a bit of work to pump the water and prepare it for drinking.
So I’m going to talk about three methods of what we might consider ultralight water treatment: Aquamira, squeeze filters (Sawyer and BeFree), and the Steripen Ultralight.
Aquamira
The one that’s probably the most popular among the hardcore ultralight crowd is a chemical treatment known as Aquamira.
Aquamira is a chlorine dioxide-based water treatment chemical kit. It consists of a 2% chlorine dioxide solution (part A) that is activated by phosphoric acid (part B). The resulting activated solution acts as a water disinfectant by interrupting nutrient transport across cell walls and membranes.
How it works:
- Mix a few drops of part A with a few drops of part B (typically seven drops of each per liter of water you want to treat) in a small mixing cup.
- Wait five minutes for the solution to activate – it turns bright yellow. It may take a little longer in cold temperatures.
- Once it’s active, then you can pour that solution into your water bottle, and then wait 15 to 30 minutes before the water is ready to drink. Longer times are required for cold water, turbid water, or to inactivate cryptosporidium cysts.
The key advantage of Aquamira is that it’s compact, lightweight, and has a long shelf life (typically about four years).
The key disadvantage of Aquamira is that it does take up to 30 minutes to get clean water. And for some types of protozoan cysts like Cryptosporidium, the treatment time is around four hours.
Aquamira Notes and Tips:
- Chlorine dioxide is highly effective against Giardia and less effective against Cryptosporidium. If you suspect that your water source is contaminated with the latter, consider combining Aquamira with a filtration method (below) or use a Steripen.
- Aquamira dosing can be halved (3-4 drops per liter each of parts A and B) if you double the treatment time to 30-60 minutes. Likewise, dosing can be doubled (14 drops per liter each of parts A and B) if you need water fast (8-15 minutes). This principle is known as Chick’s Law and is a bedrock principle in water disinfection.
- The newest (since summer 2020) 1-oz Aquamira kits now ship with a closeable cap – this is useful for backpacking! If I know I’m going to walk over a creek soon, I can create my premix, stow the cup in my pocket, and then it’s activated and ready to pour in my bottle by the time I reach the creek.
- For shorter trips, repackage Aquamira parts A and B into smaller dropper bottles, but be aware that drop size in your new bottles may be different than drop size in the stock bottles, which could affect dosing.
The Squeeze Filter (Sawyer, BeFree)
The second ultralight treatment method is a lighter version of a pump-style water filter – the squeeze filter. Instead of a pump, you attach a squeeze filter to a soft or otherwise semi-flexible water bottle and squeeze the bottle to push the water through the filter. Or, you can suck water through the filter, but that requires more effort.
There are two popular types of squeeze filters: the Sawyer Squeeze and the Katadyn BeFree. You can attach a Sawyer Squeeze directly to a Smartwater bottle. This option is popular among thru-hikers. The Katadyn BeFree filter is compatible with HydraPak bottles (like the new HydraPak Flux), making it adaptable to a variety of bottle shapes and sizes.
The flow rate of squeeze filters is relatively fast when compared to pump filters and straw filters. So unlike some of the earlier straw filters and other bottle filters, you don’t get cheek fatigue caused by sucking through a slow-flow filter.
Squeeze filters are one of my favorite water treatment solutions because I get drinkable water right away. If I know I’m going to be in an area where there’s a lot of water, I don’t have to pack any water at all in my backpack. I can just take my squeeze bottle, dip it whenever I reach a stream or lake, and hydrate at those locations.
If you need to carry more water in your pack and you’re using a squeeze filter system, then you can just take a dirty water bottle as extra water storage. When it comes time to drink, and you’re away from a water source, you can pour the dirty water into the squeeze filter bottle and then drink through the filter.
Alternatively, if you want to keep a water bottle as a clean water bottle and don’t want to drink through the filter, you can filter the water through the filter into your clean water bottle and then drink straight from the clean water bottle when convenient.
Squeeze Filter Notes and Tips:
- Flush a solution containing a few drops of chlorine bleach in a liter of water through the filter before storage. This minimizes bacterial growth in the filter, which can cause pore clogging. If you’re on a long trip, do this every couple of days.
- Make sure water is expelled from the filter before you go to bed at night, and store the filter in your sleeping bag if you expect freezing temperatures. Water turning into ice in the filter could cause damage to the filter membrane.
Steripen
The third option I want to discuss is an ultraviolet (UV) light pen, specifically the Katadyn Steripen Ultralight.
Ultraviolet light disinfects bacteria, viruses, and protozoa. And it’s very effective against all three, and it works fast. Water only needs to be exposed to this lamp for about 60 seconds to be purified. UV light works by damaging DNA inside a cell, which prevents it from replicating. So even if you ingest live pathogens, they won’t be able to reproduce in your body to a level that causes a gastrointestinal infection.
Of course, the disadvantage is that it’s a battery-operated electronic device and is subject to all the failures of such devices when you’re in the backcountry. The Steripen Ultralight is USB rechargeable. I carry a battery pack on longer trips so I can recharge the Steripen (as well as my headlamp, smartphone, and inReach Mini). But generally, the internal battery of the Steripen Ultralight remains charged for 3-7 days, depending on how often I’m using it.
When I use a Steripen, I have an old Platypus bottle that I repurposed as a dipping and treatment cup. It’s very light (< 0.5 oz!) and folds flat, so I can keep both the Steripen and the old Platy cup handy in my accessory pouch without taking off my pack.
One of my favorite features of the Steripen Ultralight is its automatic switch. It turns on automatically as soon as you dip the Steripen’s lamp below the waterline of your treatment container. There are two metal contacts there. As soon as water touches both of those contacts, the lamp turns on. Treat the water for 60 seconds (a built-in time shuts off the light automatically), and it’s ready to drink.
The other thing I like about the Steripen Ultralight is that because this is such a compact device with a short lamp, it works great in solo-size cooking mugs. I use it regularly with my Vargo Ti Bot 700Â and MSR Titan Kettle.
Steripen Notes and Tips:
- In cold temperatures, keep the Steripen inside your jacket and sleeping bag to prolong battery life.
- Make sure the USB port battery door is secure to prevent water entry into the port.
- If you regularly use store-bought water bottles like Smartwater, use the Steripen Ultra instead of the Steripen Ultralight. The Ultra is designed specifically to be compatible with narrow-mouth water bottles.
Summary
The following table summarizes each of these three treatment methods.
| Aquamira | Katadyn Befree | Steripen Ultralight | |
|---|---|---|---|
| Weight | 3.0 oz (88 g) | 2.1 oz (60 g) | 2.6 oz (74 g) |
| MSRP | $15 | $40 | $90 |
| Key Advantage | small size | fastest | most effective |
| Key Disadvantage | slowest | bulkiest | most expensive |
Facebook Live Q&A
October 17, 2020:
Where to Buy
Use our GearFinder Search Engine to shop for the best prices on Aquamira, BeFree, Sawyer Squeeze, or the Steripen Ultralight at online retailers.
Related
- Review: Katadyn BeFree Filter
- Review: Hydrapak Flux Bottle
- Skills: make your water treatment process more efficient on the trail with an accessory pouch
New PDF Download: Get our water treatment recommendations.
DISCLOSURE (Updated April 9, 2024)
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Discussion
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The purpose of this article is to present three ultralight water treatment options for backpacking. We chose these three for their diversity and efficacy, and they include a chemical method, a physical method, and an electro-ultraviolet method. We included a video to demonstrate each technology in the field.
We’ll host a Live Facebook Q&A on the topic of backcountry water treatment this morning at 11 AM US Mountain Time.
Any updates on when we might see a UV-C LED Steripen? Products like the LARQ bottle already use UV-C LED for water treatment, but that’s a heavy, stainless steel bottle that isn’t great for backpacking.
Advantages of LED should include better battery life, slightly more compact size, and no mercury. I’m surprised Katadyn hasn’t adopted them already.
^^ Hadn’t heard of the Larq so I did some quick checking. Couldn’t find a specific spec for battery life but did get this on a search for “battery life larq adventure mode”
Thanks for this. A few years ago I got sick using a probably dysfunctioning 2 year old MSR filter and Aquamira but using it wrong. Squinting at directions on the tiny bottle that had no dropper function? 1. I somehow missed looking for the yellow color. 2. I ended up making an error that I thought was correct because the instructions were not user friendly. Normally I think when it’s feasible as we do something we have a wait time we will read and re-read the instuctions.  The MSR filter? Or my Sawyer or any filter. What happens to them if you don’t use them for a year? How to store them? When to decide I’d better replace them
Also I wrote MSR and Aquamira about what happened. They never responded. I find that to be inexcusable. I wasn’t accusing them, I just wanted to know what went wrong. Except for terrific articles like this one almost all the information on these systems is PR happy talk. (You know, like on Amazon when you want to know more so you click on the video and it’s complete crap.”Here at Eff-You corp we’re making great strides to provide you the customer with the most up to date…..” Or a cute young person in khakis stands at a table and talks about this piece of back-country gear.)    Thanks again
As I posted on the live video of this topic my two-part solution is:
1. Katadyn chlorine dioxide tablets (I eschew Aqua Mira liquid)
2. SteriPen Adventurer UV wand
Both of these are classified by the FDA as purifiers.
In addition I use #2 coffee filters for times when the water may have some solids floating in it like bugs, leaves, etc. Â I am DONE with regular filters.
I love my steri-pens and have used them 90% of the time in the last decade with fantastic results, BUT their customer service is THE WORST EVER. I had several failures with the lamps and all I wanted was a repair for this hundred dollar item and sent them videos of the failure to perform in action and got NO RESPONSE AT ALL. So I quit buying them. I will not support a company that will not back their product. Now I just strain the water with a clean bandanna and use Aqua tabs.
I think Ryan validated my thoughts on Aqua Mira vs just tabs; I don’t see the infatuation with it- it’s heavier, bulkier and clearly a lot more fuss than throwing a tab in a bottle.
He did point out that per treatment it’s cheaper per dose than tablets- I’ll take the money hit for lighter weight and a LOT less fuss
I did recently purchase a Ultralight Steripen (rechargeable)- if it works as well as my Adventurer, I’ll be very happy :)
Great info here, Ryan. I never see MicroPur discussed as a chemical option. I have used it for years without problems. That is what the BSA gives scouts at Philmont. No mixing. Lightweight. Is it as effective as Aquamira??
@dorino12 MicroPur are chlorine dioxide tablets so would be as effective as Aquamira, just more expensive as he noted.
DM’s comments on Steri-Pen’s TOTAL lack of customer service is bad.
If and when my SP Adventurer dies I’ll look for another brand of UV purifier – if one exists.
The Steripen company used to have wonderful customer service, really,
Then Katadyn bought the company.
Thus it goes.
Cheers
Hey does anyone know if the Steripen Ultra makes a seal in a Gatorade bottle?
I keep coming back to my Steripen. I like the fact that I don’t have to get my hands wet and freezing cold as opposed to most filters, not to mention the super-annoying diminished flow factor of filters.
I just drop it into a 550 ml pot. No need to seal it to any bottle.
Yeah. I want to try a Steripen but I like the idea of treating in my preferred drinking bottle, which oscillates between Smartwater and Gaterade bottles rather than juggling a bottle, the Steripen and a cookpot or cut down Platy like Ryan suggests.
I’ve been using Aquamira drops since the mid 2000’s but would love something better. I tried a Steripen in ~2009 or 2010 and it failed on me the first time in the field, so I decided I didn’t want to rely on something that used batteries for something as crucial as water. I tried a Sawyer Micro a couple of years ago and it’s flow decreased quickly even with Sierra water. It did so much so that by the end of the trip I was drinking mostly untreated water and only using the filter on sources I felt most suspect.  It was also awkward as it was really tall on top of an already awkwardly tall smartwater bottle.
Like you my preferred water bottle is a Gatorade bottle, which of course doesn’t work well with a filter or steripen.
I did pick up a Steripen Adventurer Opti used for cheap last year to try a Steripen again but of course it only works with wide mouth (Nalgene style) bottles so I haven’t used it on anything other then some dayhikes.
I keep going back to Aquamira but I’m not happy with it. I hate the wait (both for the mix and the water treatment) and the taste, which is noticeably worse in some water then others for whatever reason. That being said, I’ve yet to find anything better in over a decade.
I have been using MicroPur for nearly 15 years. I love the simplicity and convenience. Yeah, it’s a little expensive but so simple to use – no mix, no mess. Even teens (i.e., boy scouts) can’t screw it up. It takes about 30 minutes before you can drink the water but that’s not a problem if you plan your water needs.
I used the Sawyer Squeeze the past 2 summers for week long scout high adventure trips to Boundary Waters and Isle Royale. We took 3 filters for 9 people, flushed each filter every day and noticed no loss of flow rate. We used the same filters both summers. (Daily flushing really is the key to sustained performance.) We opted for the Squeeze over the Micro based on guidance from an AT thru hiker who said it was worth the extra ounce for the performance of the squeeze. (My son used to use the Micro until he saw my Squeeze – the flowrate difference is quite noticeable.) Tip: dump the Sawyer bags and get Vecto bags – so much easier to fill and use for groups.
I have also used the Steripen Adventurer with a group of scouts on a week long backpacking trip to the Adirondacks. I chose this model because I could take backup batteries so we always had power. By the end of the trip we quit using the Steripen because MicroPur was so much simpler. Fill up your water, dump in a tablet and go vs. the Steripen where you have to sit there and stir your water for a few minutes. Never used the Steripen again. The Sawyer Squeeze or MicroPur for me!!
I use a Steripen Ultralight and treat water in an old Mountain House bag (I pack this along anyway to use as a scoop for filling up Platypus bladders in camp). It’s been reliable for me, and I don’t see the scoop as a hassle. This lets me use whatever bottle I want. Chemicals require a wait, especially if crypto is a concern, but I have them as a backup and I use them to treat water overnight.
This year, I went back to using my Steripen Adventurer with a wide-mouth bottle. Currently, my two favorite bottles are a peanut butter jar (1.5 oz) that holds .5L of water and a Planters Peanut jar (1.6 oz) that holds .75 L. Either is easily retrieved and replaced into the the bottom side pocket of my Mariposa without taking off the pack.  Micropur tablets are my back up, though I haven’t had to use them.
One of the wide mouth “milky” Nalgenes is 3.8oz for a 32oz bottle. That’s compared to 1.8oz for a 32oz Gatorade bottle.
Let’s try this a different way: does anyone have a Steripen Ultra handy? I’m curious about the min/max diameter of the tapered part.
I do use a Steripen Classic3 when I need to treat water. But I see the whole thing rather differently.
I am a little puzzled about the claimed need to be able to get stuff out of the pack to treat a bottle of water almost at the run. If we need to stop to take on water in the middle of the day – which is pretty rare anyhow, we welcome the opportunity to sit down and rest for a few minutes while I treat the water in my cooking pot.
Then after that brief rest we set off again, somewhat recharged. At the end of the day I don’t think any such little stop has any effect on how far we have traveled. In fact, we often find such a little stop to be part of the day.
Cheers
That’s a funny answer to what is the diameter of a thing?
Yeah, a bit OT, but it happens.
Cheers
That was a good article.
We blessed with a wealth of anecdotal reports what can go wrong with our water treatment: filters clogging, or using them in freezing temperatures, Steri-Pen’ failures and the even worse failure of their support, and the inconvenience of waiting for AquaMira to sanitize our water.
My current but no longer used is the HikerPro. My last hike I carried AquaMira for the first time and it’s ok – just a little fiddly. If I understood correctly, doubling the dose halves the treatment time, so with the freezing water I did just that. Didn’t mind the taste at all. I really like the compactness of it.
After this AquaMira runs out, I guess I’ll try either of the 2 tablet options, and I don’t see myself going back to anything more than a coffee filter and chemical treatment.
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