The Steripen Sidewinder is a hand powered unit that purifies water with UV light. Being hand powered means you can use the unit when there is no electrify, and no batteries required. The SteriPen website claims the UV bulb is supposed to be good for 8,000 one liter treatments. 8,000 liters is an estimated 2,116 gallons.
Fill the included water bottle, then crank the handle for 90 seconds. If you are not cranking fast enough, there are two LEDs that will flash red. When the 90 seconds of cranking has been achieved, the LEDs will flash green.
Instead of cranking for a full 90 seconds, you can crank for 30 seconds, swirl the unit, crank for 30 seconds, swirl the unit, crank for 30 seconds, swirl the unit. the SteriPen website says not to pause between cranking for more then about 6 or 7 seconds.
Difference between water filter and water purifier: