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Reviews > Water Treatment > Ultraviolet > SteriPEN Adventurer Opti > Owner Review by Bob Dorenfeld

SteriPEN Adventurer Opti
Owner Review
By Bob Dorenfeld
September 8 , 2013

                   Tester Information
NAME:  Bob Dorenfeld
EMAIL:  geartest(at)sageandspruce(dot)net
AGE:  55
LOCATION:  Salida, Colorado, USA
HEIGHT:  5' 6" (1.7 m)
WEIGHT:  135 lb (61 kg)

I'm an active hiker, snowshoer, skier, backpacker, amateur geographer and naturalist. Home base is the Southern Colorado Rockies, where I usually journey from 7000 ft (2100 m) to above treeline, with occasional desert trips to lower altitudes. Six to 12 miles (10 to 20 km) hiking in a day is my norm, including elevation change of as much as 4000 ft (1200 m) in a day. Most of my backpack trips are two or three nights, sometimes longer. Often I hike off-trail on challenging talus, snowfields, or willow brakes, with occasional bouldering.

Product Information & Specifications

SteriPEN Adventurer Opti
Photo: SteriPEN
Year of Manufacture2013
Listed Weight3.8 oz (108 g)
Measured Weight3.8 oz (108 g)
MaterialPlastic, Glass, Metal
Listed Dimensions(LxWxH): 6.1" (15.5cm) x 1.5" (3.3cm) x 1" (2.2cm)
Batteries IncludedYes
Treatment Volume1 L or 0.5 L
Stated Battery LifeDisposable - 50 treatments of 1 L
Rechargeable - 30 treatments of 1 L
UV Lamp Life8,000 Treatments
Minimum Bottle Diameter1.4 inches (35mm)
Battery TypeCR123 or RCR123
Carry Case IncludedYes


The SteriPEN Adventurer Opti is a tool for purifying water in the field, or anywhere a hiker or traveler wants to ensure his water is safe to drink.  It uses UV (ultraviolet) light to kill most potentially dangerous microorganisms in the water sample.  According to SteriPEN's website, it destroys "more than 99.9 percent of bacteria, viruses and protozoan cysts such as giardia and cryptosporidia" (detailed descriptions of the microorganisms can be found at the site).  UV technology has been used for many years in municipal water treatment systems, and is recognized by the United States Environmental Protection Agency as a proven, effective means of treating water.  (However, see caveats below in the Verifying Purification section).  This handheld tool is portable and lightweight, with a built-in flashlight for use when not using the purifying feature.   The business end of the Opti has two lights - the long one emits both UV and visible light when used to purify water, and the small short lamp is the flashlight.  Designed for either 0.5 L or 1 L per use, a verifying circuit ensures that the Opti is immersed correctly in the water during use, and an indicator lamp verifies that treatment completes successfully.  One pair of CR123 batteries is claimed to treat about 50 L; CR123s are a readily-available higher-voltage battery used in many types of portable electronic equipment, similar to but shorter than an AA battery.  The Opti comes with a complete set of instructions on use, care, battery replacement, and precautions, which I found both informative and easy to follow.

Field Use

I have had my SteriPEN Adventurer Opti for about a year, and have used it to treat 30 L, at air temperatures from about 40 to 85 F (4 to 29 C), water temperatures from about 35 to 50 F (2 to 10 C), and at altitudes from 6000 to 12900 ft (1830 to 3930 m).  My main motivation for purchasing this tool was to have a reliable backup for water purification on day hikes without carrying my usual larger and heavier ceramic-filter pump.  Although at first skeptical about relying on batteries, I have used the Opti enough to feel confident that it works as SteriPEN claims.

Edge ViewOpti in Operation
Edge view of Opti showing brief instructions, control button, indicator light below buttonThe Opti in operation on 1 L of water

Using the Adventurer Opti

Just about any shape or type of container will work - clear, translucent, or colored plastic, metal, or fabric such as nylon.  Make sure to estimate either 0.5 or 1 L before you start (if I'm not sure about measuring the smaller amount I'll just use the tool's 1 L setting).   First remove the clear plastic cover from the head of the Opti (can leave on when using flashlight only).  Firmly press the handle's button once to treat 1 L or twice to treat 0.5 L.  The handle's indicator lamp will flash green for about 15 seconds during which time I'll insert the tool's head into the water container to about 1 in (2.5 cm) above the light tube. A subtle blue visible light from the long tube will indicate that the UV is operating.  Gently stir the tool in the water, helping to distribute the UV light around it.  SteriPEN says that much UV reflects off the top surface of the water, which not only helps purify the water but keeps the UV out of my eyes.  There is a continuity circuit where the lamp connects to the tool's handle that will notify the user if the tool is pulled out of the water too soon - the indicator light will flash red, meaning an unsuccessful treatment.  In that case, just wait a few seconds for the Opti to reset, then start over and retreat the water.  When the treatment is finished, the immersed tube's light will go out, and the indicator lamp will turn to steady green.

For a treatment container I usually use a soft nylon collapsible bowl, like those sold for dog water (see photo).  It's lightweight, and the black interior has the advantage of providing some shade to let me see the Opti's pale-blue operation light even in direct sun.  I have also used clear and translucent plastic containers like water bottles and bladders, but in bright sun both the immersed lamp's light and the handle's indicator lamp are very difficult to see.  One precaution to be aware of is that the inside areas of the water container above the water line will not be purified by the UV light, so I like to fill my containers almost to the brim, and while operating I swirl the Opti enough to so that the water will contact that upper inside surface, ensuring that when I pour off the water into my larger water bladder (or cooking pot) the water I use is not contaminated by the untreated container edge.

Except in bright sunlight, I found the Opti to be very easy to use.  Even under conditions of bright sun, though, I can just time the treatment, and on removal of the tool from the water I'll cup the handle to shade the indicator lamp and check that it's not flashing red (easier to see than the steady green).  On timing the treatments, it always took close to 90 seconds to treat 1 L (I rarely treat less than that amount).

When done, I gently wipe off excess water from the business end and replace the Opti in its accompanying neoprene case.  The case is fairly durable, and has room for a folded-up copy of the operating instructions so that in the field I can recall how it works or error codes if necessary.  It also has a hook-and-loop belt loop to easily attach to my belt.

Problems with the Adventurer Opti

I've only had one problem so far with my Opti.  I'm still using the pair of batteries that came with it, but have been logging the amount of water treated.  At around 25 L, on a backpacking trip, I was unable to finish any 1 L treatments because after about 15 seconds of immersion the handle lamp would flash red.  Since I always carry iodine tablets as a final fallback, I disinfected my water and boiled it for the rest of my trip.  Consulting the instructions, the flashing red lamp seemed to be a sign of failing batteries, which made sense since I had no idea how old the included batteries were. However, after returning home and removing/reinserting the batteries, my Opti is working normally now, so I'll attribute the problem to incorrectly-seated batteries.  Even so, I'll be carrying a spare set of batteries for now, especially since at 30 L I'm getting up towards the maximum stated life of 50 L for a set of non-rechargeable CR123 batteries.

Flashlight Function

In addition to purifying water, the Opti comes with a flashlight built into the front next to the UV tube; no need to remove the clear plastic cover.  To operate, press and hold the activation button on the handle for 3 seconds.  The light will stay on for two minutes, or press the button again to turn it off.  The Opti UV will not function to purify water when the flashlight is on.  I've only used the flashlight once when in the field, since I always have another source of light at camp or when down at the creek getting water.  I prefer not to deplete the Opti's batteries with the flashlight, but for an emergency I'm glad it's available.

Additional Battery Notes and Cost of Operation

I'm using non-rechargeable batteries in my Opti, but SteriPEN advises that if using rechargeable CR123s, the low-battery function may not work because of the way rechargeable batteries monitor low-voltage conditions; I will stay with non-rechargeable batteries for now.  I found that the price of CR123 batteries varies quite a lot:  from a high of US$16/pair at my local hardware store, to US$1 each from a web-based retailer (non-rechargeable), so the cost of one 1 L treatment varies from a high of US$0.32 to a low of US$0.04.  For comparison, a typical ceramic filter for a hand-held water pump costs US$40, and is good for 200 L resulting in US$0.20 per liter.  Thus the Opti's cost of operation is right in league with other comparable technologies.

Other Operation Notes

SteriPEN suggests that batteries be warmed before use if exposed to below freezing temperatures -  a couple of minutes in my pocket would be enough to warm them, depending on how cold they got.  Gentle agitation while immersed in the water is not strictly necessary but is highly recommended to ensure that all water is exposed to enough UV light to purify it.  SteriPEN also suggests that if storing the Adventurer Opti for long periods it's best to remove the batteries and store them separately to avoid possible corrosion, internal contact damage, and draining of the batteries - which is what I do for just about any portable electronic device.  It's also important to note that like other types of water treatment methods, UV light works best in clear and almost-clear water; thus turbid or cloudy water needs to be either prefiltered mechanically or allowed to settle out first before using the Opti.  However, if murky water is unavoidable SteriPEN suggests using two treatments for your volume of water.

The Opti is not intended to be waterproof, only water resistant, especially the battery case.  I once dropped mine into my collapsible water bowl, but there was no evidence of moisture inside the battery case.  However, if I had any doubt I'd want to open the case and thoroughly air it out before storing or using again.

There is a long list of warnings and precautions in the instructions - most are common sense but some are not so obvious to the casual user and I've found it's worth reading these warnings occasionally, as well as the entire instruction set once in a while (especially if I haven't used the Opti frequently through the season).

Verifying Purification

It would be both time-consuming and expensive for me as an individual user to verify that the Opti actually purifies my water samples to the level that SteriPEN claims.  However, I am reasonably confident that it works as claimed, given that I use it as directed.  The following statement may be found on SteriPEN's website: "SteriPEN products have been tested by the Water Quality Association (WQA) against the US EPA Microbiological Water Purifier Standard. SteriPEN has received the WQA’s Gold Seal, certifying that SteriPEN purifies water safely and effectively".   In addition, a useful summary of water purification methods and effectiveness is published by the Centers for Disease Control and Prevention (CDC), "Drinking Water Treatment and Sanitation for Backcountry & Travel Use".  In this document UV treatment is listed only as a general treatment and not rated specifically for individual types of pathogens (protozoa, bacteria, viruses), mainly because according to the CDC not enough independent testing has been done for this method.  If I wanted complete confidence that my water was clean, I'd either combine filtration with disinfection or UV, or boil my water: CDC recommends these treatments for "very high effectiveness".

 Final Thoughts

I'm satisfied with my Opti purifier where I use it primarily on hikes.  It's lightweight and easy to use, and its small size makes it easy to store in either my daypack or backpack.   Although I haven't run out the original batteries yet, I'll keep a spare pair with me just in case the expected battery lifetime is less than stated.  Both initial cost of the Opti and operating costs are comparable to ceramic water filters, making it a good all-around choice for camping and backpacking.  Nonetheless, where water supplies are really suspect, I believe combining treatment methods is a good idea.

Reviewed By
Bob Dorenfeld
Southern Colorado Rocky Mountains

Read more gear reviews by Bob Dorenfeld

Reviews > Water Treatment > Ultraviolet > SteriPEN Adventurer Opti > Owner Review by Bob Dorenfeld

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