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SteriPEN vs H2O Amigo: A Long Distance Hiker’s Comparison

Cutting-edge solar-powered UV water purification or simple gravity filter? I took both on the CDT to compare/contrast their performance, durability, and usage.

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by Dan Feldman | 2011-03-08 00:05:00-07


The SteriPEN Adventurer Opti and the H2O Amigo Pro are both innovative and effective means for treating water in the backcountry, but the two products otherwise share little in common.

SteriPEN’s story has been one of overwhelming success and rapid adoption amongst backpackers. After selling its first unit in 1999, Hydro-Photon Inc, the makers of SteriPEN, now offer no fewer than ten versions of the SteriPEN and market not only to the backpacking community, but also to the military, emergency rescue agencies, and the general traveling public.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 1
SteriPEN in solar case.

The success and attention surrounding SteriPEN lies in a breakthrough, and admittedly glitzy concept in water purification: the use of ultraviolet light from a handheld pen-shaped device to scramble the genetic material of water-borne pathogens, making them incapable of reproducing. This technology is a clean alternative to more traditional water treatment methods involving chemicals or filtration. The Adventurer Opti is the ultralight version of the SteriPEN and can be used with disposable or rechargeable CR123 Li-ion batteries. For those not keen on buying disposable batteries or relying on the power grid, SteriPEN makes a solar charging case exclusively for the Adventurer Opti.

The H2O Amigo occupies the more subdued realm of the gravity filter. Far from being on technology’s cutting edge, the gravity filter’s basic but effective design uses a water-holding bag that contains a filter with a small tube at the bottom for water output. The bag is filled, hung, and water moves passively from the bag, through the filter, and out to another bag or a drinking bottle for consumption. It’s essentially pump filtration without all the work of actually pumping.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 2
Amigo full setup.

A quick-drying, lightweight SilNylon bag with durable drawstrings and a single open-ended output hose make the Amigo perhaps the most no-frills, elegantly designed gravity filter to date. Sadly, the Amigo is no longer in production by its manufacturer, Ultralight Adventure Equipment. MSR, Katadyn, Cascade Designs, and Sawyer Products sell their own gravity filters, but none match the lightweight simplicity of the Amigo. Used Amigos can still occasionally be found online, but these tend to be few and far between. More importantly though, the Amigo’s simple design and obtainable raw materials permit at-home construction. This subject has been discussed in great detail on BPL’s own forums.

The aim of this study was to compare the solar-powered SteriPEN Adventurer Opti with the H2O Amigo Pro for use in long distance hiking. Both devices were used alternately along 800 miles of the Montana section of the Continental Divide Trail from July 19 to September 28, 2010 to provide drinking water for a companion and myself. While one device was in use, we shipped the other ahead to a mail drop location. Once at the mail drop, we switched devices, shipping the other ahead to the next mail drop. Practical considerations for long distance hiking for each device were noted. These included observations and recorded data on each device’s weight, cost, performance, maintenance requirements, durability, and ease of lightweight modification. Temperatures ranged from the mid 80s to the mid 20s F. The Amigo was outfitted with a new Katadyn Hiker filter.



A total of 71.5 liters of water were treated with the Amigo and 107.0 liters with the SteriPEN. We primarily sourced from clear bodies of water with good flow. We occasionally got water out of lakes or from cattle contaminated sources, but never needed to pre-filter. Except for the initial charge, which was done using the supplied power adapter, the SteriPEN was charged in the field using the solar charger. Batteries were not removed from the SteriPEN when placed into the bounce box for shipping.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 3
SteriPEN solar case.

Speed and Water Quality

Both devices produced clean tasting water and neither of us became ill. They provided water in a timely fashion with neither exceeding two minutes per liter, unless the SteriPEN’s battery ran out mid-treatment. At the end of the trip, both devices were tested with clean tap water. The Amigo made one liter in 73 seconds and the SteriPEN in 93 seconds. Priming the Amigo’s filter by sucking water through the output hose was necessary in order to start the flow of water.


We appreciated the hands-off nature of the Amigo. Being able to fill the bag and hang the Amigo from a tree branch or rock while we went about other chores or relaxed was a big plus. We did need to be careful to make sure our Platypus was placed carefully under the Amigo’s output hose so that it wouldn’t tip over as it filled. The SteriPEN, requiring constant stirring for about 90 seconds per liter, was obviously more hands-on. This was not too bothersome for small quantities, but when we wanted to make multiple liters, sitting and stirring started to become tedious and, in cold, wet weather, fairly unpleasant.

Since we carried small-mouthed collapsible 2L bottles, we were not able to treat our water directly with SteriPEN, which better accommodates a wide-mouthed receptacle. However, we were able to avoid packing an extra bottle by putting water to be treated in our cook pot, and treating the water there. We did find it somewhat inconvenient to have to dig out our cook pot each time we wanted to treat water.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 4
SteriPEN in pot.

We found that the Amigo was easy to pack and I usually kept it near the top of my Granite Gear Vapor Trail pack. The SteriPEN, while in its charger case, was a little more cumbersome. As we were in Montana and thus often walking in partial or full sun, it made sense to carry the solar charging case outside and on top of my pack. The case was, however, sometimes a challenge to secure. The case’s plastic belt-style clip fit quite loosely onto my pack straps and was therefore not very reliable to use. I eventually settled on lashing the charger down using the two cross straps at the top of the pack, although this was still a loose attachment when my pack was not full.

We did not use the flashlight function on the SteriPEN.


SteriPEN’s published manual advises users to remove batteries from the device when not in use. We learned this lesson the hard way. When putting the SteriPEN away for a few weeks, we failed to remove the batteries from the device. With the second set of batteries just partially charged, we found ourselves constantly changing the batteries back and forth when the device returned to use. The set of batteries that were inside the SteriPEN had mostly discharged, and the charge left in the second battery set was only enough to treat 3-4 liters. Coupled with a few cloudy days on the trail, we never were able to fully charge one set of batteries,and thus had to keep switching back and forth between partially charged batteries. We were not able to fully charge the batteries until we stopped in town for a few very sunny days.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 5
SteriPEN on/off.

We did not have any reliability issues with the Amigo, except once when we left water in the device overnight and temps dropped below freezing. The next morning, we had to wait until the ice in the filter and hose thawed until we could treat water. From then on, we made sure to completely drain and dry (if possible) the Amigo each night.


The advantage to both devices is that they require very little maintenance. Because we used the Amigo in mostly clear water, we never needed to scrub the filter. With greater use, I expect we would have needed to scrub at some point. The SteriPEN required zero maintenance.


Despite both devices having sensitive components, neither broke or malfunctioned. For the SteriPEN, the sensitive component is the bulb, which is encased in glass. If this breaks, the only method of repair is to send the device back to the manufacturer. The SteriPEN took a tumble off my pack on several occasions, but was well-protected inside the solar charging case and no damage was done. The case itself began to show small signs of wear by the end of the trip as some of the inner padding near the latching mechanism began to get caught in the latch. With a few weeks remaining, the belt clip on the back of the case snapped off. This didn’t bother us because we found the clip to not be very useful in the first place.

The sensitive component of the Amigo is the SilNylon bag that holds water for filtering. The SilNylon is thin and thus susceptible to tearing on sharp branches. On a prior trip, I actually made a small hole in the bag this way, but was able to easily repair the bag with SilNet sealer.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 6
Amigo Bag - a closer look.

Weight and Volume: (See Figure 1)

At 3.75 oz on a kitchen scale, the SteriPEN Adventurer Opti with a single set of batteries is significantly lighter than the Amigo, which comes in at 7.75 oz of dry weight. However, the solar charging case, with its necessary second set of batteries, brings the SteriPEN system up to 11.0 oz. This combination is .25 oz heavier than a soaking wet Amigo stored in its SilNylon carrying bag.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 7
Figure 1

  Weight (oz)
SteriPen w/ single pair rechargeable batteries 3.75
Steripen w/ solar case and 2 battery sets 11.00
H2O Amigo, dry 7.75
H2O Amigo, wet 10.00
H2O Amigo, dry w/ bag 8.50
H2O Amigo, wet w/ bag 10.75

The H2O Amigo in its SilNylon bag compresses down to 75 in³ and takes up twice as much pack space as the 37 in³ solar charging case. This was a moot point for us as we carried the SteriPEN in its solar charger outside of my pack.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 8
Amigo wrapped.

Cost (see figure 2)

While the SteriPEN with a solar charger is initially more expensive, the H2O Amigo Pro surpasses it in cost after approximately 2,500 liters of water has been treated. WAt this point the Amigo’s Katadyn filter will need to be replaced for a third time. Taking this into consideration, the SteriPEN becomes an increasingly better value for the amount of water treated. Interestingly, the H2O Amigo eventually even surpasses the cost of using the SteriPEN with disposable batteries.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 9
Figure 2

  0L 1000L 2000L 3000L 4000L 5000L 6000L 7000L 8000L 9000L 10000L
SteriPEN Opti w/ Rech. Batteries $150.00 $150.00 $150.00 $150.00 $150.00 $150.00 $150.00 $150.00 $170.00 $181.88 $181.88
SteriPEN Opti w/ Disp. Batteries $100.00 $135.72 $173.32 $210.92 $248.52 $286.12 $323.72 $361.32 $418.92 $456.52 $494.12
H2O Amigo $50.00 $90.00 $130.00 $170.00 $250.00 $290.00 $330.00 $410.00 $450.00 $490.00 $570.00

Certain performance assumptions were made in these calculations. With the exception of liters water treated per charge for the SteriPEN, field-testing did not provide sufficient volumes of water to test capacities experimentally:

  • The SteriPEN rechargeable batteries die after 300 charges. Source: SteriPEN customer service. Field-testing on the CDT revealed that these batteries, new and fully charged, made 28 liters of water.
  • A pair of CR123 Li-ion disposable batteries are capable of treating 50 liters of water before needing replacement. Source: SteriPEN User’s manual.
  • The SteriPEN’s bulb requires replacement after 8,000 liters of water treated. Source: SteriPEN customer service and user’s manual.
  • The Katadyn filter is capable of treating 750 liters of water before requiring replacement. Frequent treatment of murky water and failure to periodically clean the filter will obviously shorten this lifespan. Source: Katadyn product manual.

Cost Assumptions (not including tax or shipping):

  • Disposable CR123 Li-ion batteries are purchased online in quantities of 50 at a cost of $46.99 ($1.88/pair). Each battery is 3V with 1300mAh capacity.
  • Replacement rechargeable batteries are purchased online in quantities of 2 at a cost of $11.88. Each battery is 3V with 650mAh capacity.
  • Replacement Katadyn filters can be purchased online at a cost of $40.00.
  • The SteriPEN bulb can be replaced by the manufacturer at a cost of $20.00.
  • A used H2O Amigo can be obtained online for $50.00.

Ease of Lightweight Modification

Although we chose not to modify either device on this trip, both devices lend themselves to some modification to drop weight. The Amigo’s output hose can be cut to a shorter length and the small plastic hose clamp removed. The cords that allow the Amigo to be hung can be cut and re-tied. On the SteriPEN solar charger, the clip can be removed. Otherwise, the SteriPEN itself is difficult to modify. The plastic cap that protects the bulb can be omitted, but this leaves the bulb vulnerable.

SteriPEN vs H2O Amigo, a long distance hiker’s comparison - 10
Amigo output hose.

Overall Impressions

We found that by the end of our trip we preferred using the H2O Amigo. This was based on the fact that by its hands-off nature, the Amigo, especially for treating multiple liters of water, was more convenient to use and we encountered fewer problems with reliability. Admittedly, the battery issue was our own fault, but we also value not having to worry about battery charges and changes on backpacking trips.

The added convenience of the Amigo, comes with a significant difference in monetary price. However, the long term savings associated with the SteriPEN currently adds a significant cost in weight, as the solar charger with its second battery adds an extra 7.25 oz, negating the SteriPEN’s weight advantage over the Amigo. With some design changes to the SteriPEN’s solar charging feature, this would be a closer call. Reducing the size of the charging case might be a possibility. Using a lighter material to make the case would be another. This would expectedly increase the cost of the case, but since the cost savings with the solar rechargeable feature is so significant, this might not be a tough sell. Finally, designing the solar charging case to charge the batteries while still inside the SteriPEN would reduce weight by eliminating the need to carry a second set of batteries. It would also add a considerable amount of convenience to the entire system.


"SteriPEN vs H2O Amigo: A Long Distance Hiker’s Comparison," by Dan Feldman. (ISSN 1537-0364)., 2011-03-08 00:05:00-07.


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SteriPEN vs H2O Amigo, a long distance hiker’s comparison
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Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: Re: Re: Me too on 03/10/2011 02:27:25 MST Print View

Hi Chris

> everything I've read indicates the chances of getting a virus from US water sources is basically nil.
Ah, now if we transition from whether there are viruses in the water in America to whether you run much of a risk from the viruses which are present - that is a huge world of difference. In practice we can tolerate quite a lot of the more common sorts of virus (and bacteria). We would be dead very quickly if we couldn't.

In fact, we carry a huge load of bugs in our bodies anyhow, and are critically dependent on them for life. This is what most of the population does not seem to know, understand or believe. You are alive because of the microflora of your skin, body, gut etc. Without all those bugs you would die. So why the authorities allow some unscrupulous vendors to sell antibiotic wipes for the kitchen to the uneducated public beats me.


Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: SteriPEN vs H2O Amigo, a long distance hiker’s comparison on 03/10/2011 02:29:59 MST Print View

> Any idea of when that article might be out?

At this stage, 2011 is as much as I can say. It's another wide survey, not just the Sawyers.


Chris W
(simplespirit) - MLife

Locale: .
Re: Re: Re: Re: Re: Re: Me too on 03/10/2011 04:13:56 MST Print View

Thanks Roger. We're on the same page here. I need to work on correctly wording my posts to relay my intentions a bit better.

chris mcMaster
(ulachris) - F
ULA will be producing the H2o Amigo again on 03/10/2011 06:50:06 MST Print View

Some of you may be interested to know that ULA recently made a deal with the inventor of the h2o amigo and we now have the rights to produce it again// No time table as to exactly when it will be available, as you can imagine the next 3 months are extremely busy for us and I can assure you it won't be before early summer that we're ready to go with it again/

Ken T.
(kthompson) - MLife

Locale: All up in there
Re: Re: Re: Steripen on 03/10/2011 06:57:22 MST Print View

"Buy the batteries online. Cheap."

Of course I mean you can buy the best batteries online cheaper than in the grocery store, etc..
Battery Junction sells Energizer and Duracell for less than $2 each.

Lower quality/output batteries are what I suspect cause a majority of dissatisfaction among unexperienced users.

I have had no issues in years of use.

Ken T.
(kthompson) - MLife

Locale: All up in there
Re: ULA will be producing the H2o Amigo again on 03/10/2011 06:58:33 MST Print View

inventor of the h2o amigo

Bill F. Getting credit?

Todd Hein
(todd1960) - MLife

Locale: Coastal Southern California
Amigo Pro on 03/10/2011 07:57:07 MST Print View

I have used an Amigo Pro for several years and it works great. However, maybe I missed something, but why do a comparison using this product since it is unavailable? Maybe ULA will bring it back...

Dave -
(FamilyGuy) - F

Locale: Up there
Amigo on 03/10/2011 08:24:26 MST Print View

Isn't the Platypus Clean Stream system essentially the same as the Amigo and available now?

James Verlander
(jimver) - F
. on 03/10/2011 08:26:24 MST Print View


Edited by jimver on 10/19/2011 14:56:55 MDT.

Jim Cowdery
(james.cowdery) - MLife

Locale: Central Florida
Replacement on 03/10/2011 09:03:19 MST Print View

My daughter started with a steripen on her AT thruhike in '09. It broke about 1 month into the hike. She started using AquaMira and a bandana for a pre filter.

Steripen replaced the product and I have used it on several section hikes. It ceased working on my last section hike and I replaced it with a Platty system.

I will stick with the low tech solution.

Matthew Swierkowski
(Berserker) - F

Locale: Southeast
Batteries on 03/10/2011 10:34:27 MST Print View

RE: Ken & Roleigh

I agree with Ken in that I just bought some Duracell batteries from Battery Junction. Cost $32 for 12 (that's $20 for the batteries plus $12 for shipping...yeah that shipping is high), so that's $2.67 per battery, which is much cheaper than buying them at a local store like Wal-mart.

Roleigh, I would add Energizer to your list of high quality batteries that the manufacturer prefers as I believe that is what came in my Steripen when I bought I assume they feel those are good ones to use in it.

Tony Wong
(Valshar) - MLife

Locale: San Francisco Bay Area
Re: Amigo vs. Sawyer on 03/10/2011 13:45:32 MST Print View


They are both gravity filters, but the storage bags are quite different as is the filter technology.

I would guess that the Clean Stream is Heavier than the Amigo given that the Amigo is using a silnylon dirty water storage bag where the clean stream is using maybe something heavier.

My understanding is that the Amigo is using a Katadyn water filter that needs to be replaced over time.

The Sawyer filter is using hollow plastic tubes that are poreous enough to allow water to pass through the exterior of the tubes to the hollow center to then flow out of the filter, but those pores are too small for any bacteria to pass.

Since the Sawyer filter is using inorganic material/plastic, it does not wear out, bacteria can not grow on it, and it can be backflushed to clear clogs.

The Sawyer filter's warranty is for 1 Million gallons...effectively a life time guarantee.

The negative on the Sawyer is that it does not have any active charcoal as other filters might....compared to the Steripen, this is a non issue because the Steripen can not do anything to remove chemicals or improve taste either.

Hope this helps explain some differences.


Rick Dreher
(halfturbo) - MLife

Locale: Northernish California
Re: Amigo vs. Sawyer on 03/10/2011 14:12:49 MST Print View

Hi Tony,

Good summery of the differences and similarities. If I can be indulged one teensy-weensy detail, the Sawyer is subject to bacterial (and mildew) growth. It's almost, perhaps literally impossible to dry out and Sawyer literature direct it be sanitized with chlorine solution prior to storage.



John S.
(jshann) - F
Re: Re: Amigo vs. Sawyer on 03/10/2011 14:30:06 MST Print View

Staphylococcus epidermidis (all over you right now) loves to grow on plastic, a main reason why things like bladder catheters have to be removed/replaced every few days.

Edited by jshann on 03/10/2011 14:33:02 MST.

Tony Wong
(Valshar) - MLife

Locale: San Francisco Bay Area
Re: Amigo vs. Sawyer on 03/10/2011 15:16:42 MST Print View


Thanks for the clarification.

Would explain why the manual does talk about putting about 10 drops of chlorine into a liter of water to flush it though the system.

Anyway, I have been using mine for a number of years now 2007-2008? and it is still going strong and has not given me any problems.

Will be looking forward to seeing Roger's report on various gravity filter.


Dave -
(FamilyGuy) - F

Locale: Up there
SteriPEN vs H2O Amigo, a long distance hiker’s comparison on 03/10/2011 20:32:07 MST Print View

Yes - Tony, Rick - thanks for the clarification.

Tim Zen
(asdzxc57) - F

Locale: MI
Re: Re: Amigo vs. Sawyer on 03/10/2011 20:39:18 MST Print View

We are to assume no one became ill during the trip or two or three weeks afterward.

The units never were used on the same water, but the sample size probably makes up for this. You don't know if any of the water would have made anyone ill if left untreated (no volunteers I suppose)

So the point of the article was comparing the mechanics of using the two systems in the field. The other conclusion is the two units provide the same level of water safety.

A small (maybe micron-sized comment) don't you view charging batteries as maintenance?

Cameron Phillips
(Jean-Guille) - F

Locale: Southern California
Re: Amigo Pro on 03/10/2011 21:31:51 MST Print View

Todd, ULA is bringing the Amigo back...see the post three above yours for the post by ULA...they also have info on it on their Facebook page...

Bill Fornshell
(bfornshell) - MLife

Locale: Southern Texas
Re: Re: ULA will be producing the H2o Amigo again on 03/11/2011 07:44:47 MST Print View

inventor of the h2o amigo

Bill F. Getting credit?


What I did was change to the Katadyn Filter, reduce its weight and change the location to put it inside the water bag. Moving the Katadyn Filter's location is the only real difference between the original Amigo and the new Amigo. The filter location was my idea.

I did send the new owners of ULA an email with a link to my thread here and told them I don't know who they though invented the idea of where the filter went but they had my permission to use that part in a new product if they wanted to.

Edited by bfornshell on 03/11/2011 07:45:54 MST.

Dan Feldman
(podin04) - F
Re: Re: Re: Amigo vs. Sawyer on 03/12/2011 09:33:16 MST Print View


Nobody became ill after the trip.

You're right, the units weren't used in the same water. My suspicion is that some of the water we used, perhaps the water that was taken from cow-contaminated sources, would have made us sick. My understanding is that the incidence of backcountry water-acquired diarrhea is 3-5%, so it's always hard to say....

The point of the article was comparing the two devices for use in long distance hiking, commenting on the things long distance hikers tend to find important: convenience, cost, maintenance, etc. The two units provided the same level of water safety if your criteria is that none of us got sick. The two devices do differ in what they do and do not filter. more on that in another comment.

I personally view battery changing more as a convenience feature and maintenance as something that's done on a routine basis to prevent damage or operating failure. Yes, the SteriPen won't work if the batteries run out, so maybe this is just semantics.