Backpacking Light reviewer gives Classic 3 the green light

SteriPEN Classic 3 Field Testing

Australian Research Scientist, Roger Caffin, has been hitting the trails throughout his life and in recent years, searching for the best light-weight gear to add to his pack. After field testing SteriPEN Classic 3, Caffin shared his experience with the Backpacking Light community.


SteriPEN Classic 3: Spotlite Review

SteriPEN has heeded our pleas and its newest model continues to offer great water treatment while getting rid of some of the bugs from previous models.


We reviewed the Adventurer, the first model in the SteriPEN series, way back in Feb 2007. That was not very fast of us, as the first unit was sold in 1999. It worked fine, but had a few bugs in the early releases. The main one was that the current drain when the unit was ‘switched off’ was far too high, but that was fixed around the time of our review. There were some problems with very pure water, such as came from snow melt. The solution there was to add a few crystals of salt, to make the water slightly conductive. Mind you, if the water was that pure I would not bother treating it myself anyhow. And there were problems with people using cheap batteries – alkaline or rechargeable. The UV tube used is a bit hungry, and cheap batteries just could not hack it. Sadly, the myths and misconceptions about how the SteriPEN was not reliable were started way back then. One sometimes suspects that competitors did not like the whole idea.

The battery problem was solved by redoing the electronics plus recommending that you store the unit without the batteries. That’s always a good move with any device which does not use a genuine mechanical switch on the power supply – which is most consumer electronics these days. But getting the battery case open was a bit of a nuisance, so a MYOG thumbscrew was developed to replace the flat hard-to-operate screw.

One solution to the rest of the problems was the Adventurer Opti, currently selling around US$90 from their web site. This unit replaced the impedance sensing with a white LED sensor, which always worked. It too used CR123 batteries, with a ‘life’ of about 50 L (with brand-name batteries!). I have been using one for a number of years, and it has never let me down. Some rechargeable batteries did let me down in France this year, but I was carrying some good non-rechargeable ones as a backup, and they solved that problem very quickly. SteriPEN has released other models, such as the Emergency and the Freedom, but I suspect they did not catch on as well as the Adventurer Opti.

Other companies have forayed into the UV market, including Aquastar and Camelbak. However, they do not seem to have had much impact, which is probably just as well. As explained in our 6-part series on Water Treatment methods, the units sold by these two companies permit you to shine the UV in your face, potentially causing all sorts of medical problems. In contrast, none of the SteriPEN models will operate out of water.

Into this now 15-year-old market a new model has now been released: the SteriPEN Classic 3, which we review here. It’s a bit cheaper, at US$70 on their web site.

What are the Hazards?

In principle there are many hazards to be found in water. We can have the usual bugs such as viruses, bacteria and protozoa. There are also larger ‘things’ such as helminths (‘worms’) and some toxic algae are to be found in water in some places. You can also find dissolved chemicals coming from domestic, agricultural and industrial sources. Finally and not so commonly understood, there are pharmaceuticals in some waters, sometimes excreted by users and sometimes just ‘flushed’. These can include narcotics, hormones, antibiotics and more. Fortunately this last class is rarely met ‘in the mountains’.

We can try to deal with these using filters, but most of them do not handle viruses (although the very new Rapidpure ones should), and they cannot be relied on to remove many dissolved chemicals. In addition, filters block up, slow down, the bags burst, and many filters are very slow to start with and sometimes heavy. Apart from the Katadyn Hiker, most pumped filters have been a bit of a disaster. (I won’t name any particular model here for obvious legal reasons.)

Some of the bugs can be killed with chemicals, but these generally don’t deal with the larger protozoa like Giardia or Crypto – or take many hours to do so. How many people want to wait the 4 hours needed to treat Giardia bugs, as recommended for several chemicals? And quite a few people don’t like using chemicals anyhow. One cannot blame them.

UV treatment is fast (90 seconds for 1 L) and works with all bugs (it disrupts their DNA), but it needs batteries and is a bit ‘high-tech’ for some. It does not handle large ‘floaties’, but I filter those out with a handkerchief when they are too much of a problem. UV does not deal with dissolved chemicals either, but I would steer very clear of any such water: it can be dangerous stuff. There’s a creek below an abandoned silver mine here in Australia: it is known to be loaded with arsenic! Otherwise, UV works just fine.

New Features

Screenshot 2015-06-16 16.43.45

What new features has SteriPEN managed to get into the Classic 3? Well, quite a few, and they claim that they are a result of all the feedback they have been getting. Let’s list them and explain what they mean. Before we do, I’ll just add that the blue light you see coming from the glass bulb out front is just incidental visible light, not the UV radiation that kills the bugs. But it is an excellent indicator of when the unit is working – and when it has finished.

Changed water sensor: This unit reverts to the impedance sensing used in the original Adventurer, but it uses little prongs sticking out rather than flat plates. The red lines points to one of them; the other is visible behind/through the glass bulb. In itself this is not a major change, but it blends in with the next item. I suspect the change in the prongs and gasket also makes it a lot harder for the unit to be fooled by stray water on the surface – a problem which sometimes affected the original Adventurer. Being a techie from a long way back, I could not resist looking at the signal on the prongs with an oscilloscope. You see, you can’t just measure the resistance of the water between the prongs by sticking a few volts across them: you would electrolyze the water and risk fouling the prongs. That’s not so smart. Skipping over the details, there’s a complex AC waveform across the electrodes which should make sensing the water far more reliable.

SteriPEN Classic 3 water sensor and tapered neck gasket. Tapered neck gasket: This is the blue bit in the photo here. It is a slightly soft, and can be used to seal against the neck of some water bottles. It does not work with my 1.25 L PET fizzy water bottles (it’s too big), but it may work with the slightly larger ‘Gatorade’ sized bottles. You can see why the prongs fit more easily through this gasket compared to flat plates, and they poke forwards into the water in a bottle as well. A better design I think. Activate in or out of water: This is purely a change in the firmware – the program in the little microcomputer inside the thing. With the original you had to get the sequence of button presses just right or the unit would not work. I was caught a number of times. With the Classic 3 you can press the activation button before or after you put the bulb in the water: it does not matter. But the UV light won’t come on until it senses that it is IN the water.

Simpler controls: This improvement is really an extension of the previous item. There are now three little LEDs: two green ones for 1/2 and 1 L, and a separate red one. If you are color blind this might help a bit. Also, the number of button presses has been ‘rationalized’. In the older models it was 1 press for1 L and 2 presses for 1/2 L – which seemed a bit silly to me. For the Classic 3 is it 1 press per 1/2 L, so to get 1 L you press twice. And, to make sure, these instructions are written on the case. You get various flash codes from the LEDs (I got rhythm …), but all you really need to remember is that you want green flashes. However, a long green, short red, long green means your batteries are getting low: this is useful. Four greens followed by a red means you didn’t get the unit in the water soon enough – so try again. One long red means it never saw any water, while four short red flashes means you have to replace the batteries. There are others. Of course, if the lamp never lights up, something else may be faulty, so watch it.

Better battery life: They made the electronics a bit more efficient, although driving the UV tube still requires some power. The gain here would not be great compared with the load used while working. But also see under ‘AA Lithium Batteries’ below – they give the unit a much longer life in the field.

SteriPEN Classic 3 battery caseBetter battery case: This combines with the next item. The big photo above shows the battery case and the new lid; the smaller photo here shows how the lid works. The lid is large, with knurls around the edge, and you only need to twist it about 5 mm to open it. The markings show it all. Yes, there is an O-ring seal for the lid, but SteriPEN emphasis that this is for splash protection only, not submersion. Don’t drop it in the river. In the big photo you will see lots of + and – signs, which initially look very confusing. They are not really. Look closely and you will see that each battery hole has either + signs or – signs on either side of it. Figure it out once and you are done.

Use of AA lithium batteries: This is the big one in my opinion. With brand-name 2 CR123 batteries (expensive, sometimes hard to find) you get 50 L treatment (they claim). An Opti with batteries inside weighs 102 g; with one set of spare batteries 137 g. With the Opti I always carry a spare set. The Classic 3 weighs 141 g with four lithium AA batteries inside it, and the batteries are good for about 150 L treatment. The unit is supplied with four of them, by the way. Frankly, I would not bother carrying spares. If in any doubt I would swap new batteries in at home before the trip and use the old ones for my headlamps – which I am sure they would power for another year or two (or more).

Can use alkaline or rechargeable batteries: Yes, you can use alkaline batteries as well, but you will only get 50 L of treatment – or maybe a bit less, depending on the brand. With alkaline batteries loaded the unit is heavier: 178 g. With rechargeable batteries (NiMH) you might, if lucky, get 100 L, depending on the age of the batteries and how well you maintained them, but the unit will then weigh 191 g. Note that while the Lithium batteries will cope with sub-freezing temperatures, alkaline and NiMH won’t.

Battery isolator: Regardless of the greater capacity in AA batteries and the reduced off-state current, it still makes sense to either remove or isolate the batteries when the unit is not in the field. In fact, when you buy the Classic 3 it comes loaded with 4 AA batteries and a battery isolator. This is a bit of tough plastic film fitted inside the cap which isolates each battery from the contacts in the lid. It has a ‘Remove’ tag sticking outside the lid to remind you that it is there. With that in place there is no current drain at all.

SteriPEN Classic 3 lamp coverImproved bulb cover: The original bulb cover was a pain to get off. One lived in fear if I even went so far as to just slightly modify mine to make it easier to remove. Well, SteriPEN has been listening. See the wavy edge on the translucent blue bulb cover here? To remove cover you twist it off, using that wavy edge. It works really well: the cover sort-of pops off as you twist.

Pre-Filter: They also provide a prefilter unit which weighs ~45 g. There’s a little mesh filter unit (6 g) which fits into a special adapter which mates with the ‘standard’ 60 mm Nalge bottle thread. You fill your water bottle by pouring through the mesh filter, then you extract that little bit and stick the Classic 3 into the same hole in the adapter, where the soft gasket makes a seal. Well, if you are into that sort of thing then fine, but I find those sorts of 1 L water bottles are far too heavy (175 g empty) compared to my 1.25 L PET rocket-base bottles (44 g empty). Sadly, the little mesh filter by itself is too big to fit into the neck of a PET bottle.

Field Testing

SteriPEN Classic 3 Field Testing

Apart from battery life, which I discussed above, there are really just two things to consider for the Classic 3. The first is whether it works – whether it kills off the bugs. That’s an old discussion, fully explored in our previous reviews. In short, if you follow the instructions for the unit, it meets EPA requirements. The use of UV water treatment by the military and municipalities backs that up. OK, you might need to filter out the floaties – but you do that anyhow with most any system. And it does not remove dissolved chemicals – but neither do most of the competitors.

The second question is how easy is it to use. My wife usually leaves me to deal with such matters, but likes to be able to do it herself just in case. One evening I showed her the unit, packaged up with battery isolator in place and blue cover over the bulb, and told her just once what to do. OK, take battery case lid off by twisting, remove bit of plastic, replace battery case lid and lock in place. Pretty simple. Twist blue cover off – even simpler. “Do I press before I put it in the water or afterwards?” “Doesn’t matter.” So she stuck it in the water, pressed the button twice, and stirred it around. After a while (two presses, so 90 seconds) the blue glow went out and the little green LEDs flashed at her. “OK, it’s flashing green – does that mean it’s all OK?” “Yes.”

And that was it. All done. I dried the bulb (on my shirt), we replaced the blue cover over the bulb and the battery isolator under the lid, and carried on with other things. End of story.

Kinda simple, compared with faffing around with chemicals and waiting the required time, or stringing up a bag and a hose and a filter and squeezing and backflushing and …


Model: Classic 3

Batteries: 4 AA

Battery Life: Lithium batteries: ~150 L

Weight: 141 g with 4 AA lithium batteries

EPA requirements: Meets all requirements

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