With the water filtration battle heating up, it’s time to pit two of the top contenders against one another and determine who will reign as heavyweight champion. It’s going to be a battle royale. In the blue corner, weighing in at 13 oz., is the LifeStraw Mission five-liter water filter. The LifeStraw Mission is a high-volume, gravity-powered water purifier that removes viruses in addition to bacteria and protozoa to make backcountry water safe to drink.

In the red corner, weighing in at a scant 10.5 oz., is the MSR AutoFlow Microfilter. Now with an even lighter filter cartridge, the AutoFlow Microfilter represents the latest evolution of backcountry hydration, combining filtration, storage, and collection into a single, pump-free system.

Both the LifeStraw Mission and MSR AutoFlow MicroFilter use the same gravity filtration concept: collecting dirty water in a 4-5 liter bag and letting gravity do the rest by pulling the water through a hollow fiber filter and into your potable water container. Although both systems appear physically similar, there are several differences in their spec sheets and how they deliver clean drinking water that may impact the way you judge the outcome of this bout.

Round 1:

The LifeStraw Mission wins by unanimous decision in the filtration category. It is capable of removing 99.999 percent of viruses, including Rotavirus and Hepatitis A. Additionally, the Mission removes 99.9999 percent of bacteria (E. coli, etc.) and 99.99 percent of protozoa (Giardia, Cryptosporidium). The MSR AutoFlow Meets NSF protocol P231 for removal of bacteria (99.9999 percent) and protozoa (99.9 percent) from beginning to end of filter life in “worst-case” water. But there is no virus protection offered, which may or may not be a concern for your particular requirements.

Round 2:

We’re on to the flow-rate category, and the MSR delivers a devastating blow. With a flow rate of 1.75 liters/minute, you’re never waiting too long for clean drinking water. The MSR AutoFlow MicroFilter also includes a versatile adaptor cap that fits wide-mouth bottles and the company’s Dromedary bags, as well as a hose fitting that allows you to directly fill your hydration reservoir without removing it from your pack. The Mission delivers clean drinking water via a tap that flows at a much slower rate of 0.2 liters/min, so patience is key.

Round 3:

In regards to ergonomics and packability, the two contenders appear to have fought to a draw. The MSR AutoFlow is lighter and packs smaller, but the LifeStraw Mission has a more robust, larger-volume, PBA-free reservoir bag. The LifeStraw Mission also comes equipped with a better strap for hauling the bag from the water source to the campsite and hanging it.  However, the MSR AutoFlow MicroFilter utilizes a softer, more flexible hose material that reduces kinks and packs easier than the more rigid tubing supplied with the LifeStraw Mission.


You’ll have to decide which of these excellent gravity water filters should end up in your backpack for your next adventure. Both the MSR and LifeStraw use similar hollow-fiber technology in their filter elements. This form of filter needs occasional back-flushing to clean the hollow fibers, and each brand has a different method for achieving this. Pay attention to the directions, as you will need to perform this procedure in the field. These filter elements are also fragile and can be damaged while exposed to freezing temperatures.  If the water trapped inside the hollow fibers freeze, they will rupture, rendering the filter useless.

There are a few things I’m planning to change to make the LifeStraw Mission better suited for my personal needs. I prefer how the MSR delivers the clean water to various containers versus the LifeStraw Mission. I plan to swap the stiffer hoses supplied with the LifeStraw Mission in favor of 100 percent silicone food-grade hoses. I also plan to shorten the length of hose between the reservoir and filter, which will keep the filter higher off the ground and easier to manipulate while hanging from a tree. Finally, I’m going to lengthen the clean-water outlet hose and add the MSR adaptor cap to make container-filling much cleaner and easier.

Image courtesy of Erik Meisner

LifeStraw Mission specs:

  • Purifies 18,000 liters / 4,755 gallons of water to 0.02 microns (20 nm)
  • Removes virtually all bacteria (99.9999 percent), protozoa (99.99 percent), and viruses (99.999 percent) that can contaminate water
  • Exceeds U.S. Environmental Protection Agency drinking-water standards
  • Compact roll bag reservoir available in five liter (1.3 gallon) and 12 liter (3.1 gallon) sizes
  • Reduces turbidity (muddiness)
  • Flow-rate of 9-12 liters (2.4-3.2 gallons) per hour
  • Lightweight: 0.43 kg. (0.96 lbs)
  • Ultrafiltration hollow fiber membrane
  • Requires no electrical power, batteries, or replacement parts
  • Easy-to-clean pre-filter and purification cartridge
  • All raw materials are BPA-free and U.S. FDA compliant
  • No aftertaste: LifeStraw doesn’t use iodine or iodinated resin chemicals
  • Retail $119.95
  • Buy here

MSR AutoFlow Specs:

  • Testing: meets NSF protocol P231 for removal of bacteria (99.9999 percent) and protozoa (99.9 percent) from beginning to end of filter life in “worst-case” water
  • No pumping: lets gravity do the work so you don’t have to
  • Fast: filters more than 1.75 liters per minute
  • Lightweight: weighs only 10.5 oz. (299 g)
  • Field-maintainable: can be cleaned repeatedly without disassembly for flow recovery.
  • Adaptable: filter directly into most any bottle or reservoir with included Universal Bottle Adaptor
  • Retail $119.95
  • Buy here

And now for some greater good information:

For each LifeStraw product purchased, one school child in a developing country will be provided with safe drinking water for an entire school year. Visit LifeStraw® Follow the Liters, where you can see the impact of consumer contributions. There, you can follow the program’s progress by viewing the most up-to-date measurable data on program achievements and hear stories from children who have been positively impacted.

Image courtesy of LifeStraw