As a long-distance hiker and ultralight backpacker I am always looking for lightweight, reliable, and robust gear to bring into the backcountry.  In 2007, while on the Appalachian Trail, I was exposed to the original SteriPEN.  A handful of hikers were using the ultraviolet pen shaped light to purify their drinking water.  The advantages were obvious; compact and relatively lightweight, no filter that needs to be changed, and no chemical taste to the water.  The SteriPEN Classic is powered by AA batteries, making it easy to find replacements along the trail.

Not long after getting off the AT I picked up a SteriPEN Adventurer edition, which was powered by a CR123 battery.  It came with a solar charging case, which seemed like it should resolve the issue of running out of power.  I quickly abandoned the unit because the solar panels were unable to charge the batteries in a reasonable time and the unit provided an unpredictable number of treatments per charge.   The larger SteriPEN Classic still seemed like the best and most reliable choice.

The SteriPEN Ultra is the latest in the SteriPEN line.  It is a medium sized unit, measuring about 8” long by 2” in diameter, and weighing in at just over 5oz with the neoprene case.  It is powered by an internal lithium battery which charges by micro USB.  This opens the door to charging from a solar panel or USB battery.  The operation is pretty straightforward, with only one button on the unit and an OLED display.  Pressing the button will turn on the unit, once the unit is on it defaults to treatment for 1L.  The display has a little animation indicating that the unit is ready to be submersed in water.  To treat 0.5L give the main button two quick presses, a single press will switch back to 1L.  There are simple instructions printed on the front of the unit to indicate how to switch between 0.5L and 1L treatments.  The unit is able to detect when it is submersed in water and will activate the UV lamp, the display will then switch to an animation indicating that you should be stirring the water with the unit during treatment.  A counter will also be displayed indicating how long to treat the water (90sec for 1L, 48sec for 0.5L).

SteriPEN states the unit will treat 50L of water per charge.  In my tests this is an accurate number, I ran it through its passes twice, each time it treated just over 50L.  My only gripe about the unit is the inconsistency in the battery meter display.  When the unit is powered on, there are four bars at the bottom of the display to indicate battery life and after treatment the display flashes an icon of a battery with four bars in it.  The various battery indicators rarely matched up.  Admittedly, I was putting the unit through its paces, doing 50 treatments in a row.  This may have impacted the way the unit reads the amount of battery life and may not be consistent with typical use.  The bottom line is I don’t completely trust the battery meter, but that is a relatively minor issue.  What is more important is knowing you will get 50L of treatment, that should be enough water for one person for 7-10 days.  As long as you fully charge it before you head out, or are carrying a USB battery, you should have plenty of power.

Overall this is a great unit and is definitely worth looking into if you are in need of a new water treatment system.  It is a small lightweight unit that doesn’t require lots of time and energy to pump water, and as opposed to chemical treatments, the water is drinkable right away and has no chemical taste or odor.