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The MSR Trail Base Water Filter Kit is a gravity-powered water filtration kit with modular components aimed at lightweight and ultralight backpackers and other backcountry enthusiasts. Gravity-filtered systems allow a backpacker to complete other camp chores while simultaneously filtering water, saving time and energy after a long day of walking.

MSR trail base water filter kit 1
Photo: Mountain Safety Research

What makes the Trail Base system unique is its modular nature: the filter component is designed to be carried within easy reach while backpacking and can be used independently of the gravity system to filter water quickly over the course of a day.


  • Modular components
    • Trail filter
    • Gravity system
    • Clean and dirty water reservoirs
    • Connective tubing
  • Effective against bacteria
  • Effective against particulates
  • Effective against protozoa (giardia and cryptosporidium)
  • Field-cleanable
  • Replaceable filter cartridges
  • Made in the USA


MSR Provided Specs

  • Total Weight: 1 lb 6 oz / .62 kg
  • Width: 8.5 in / 12.7 cm
  • Filter Media: Hollow Fiber
  • Filter Pore Size: 0.2 Microns
  • Flow (L / min): 1 L / min
  • Flow (Squeeze / min): 60 squeeze / minute
  • Cartridge life: 1500 liters

Measured Specs

  • Total Weight: 1 lb 1.3 oz / .491 kg
    • Trail Filter Weight: 5.9 oz / 167 g
    • Dirty Water Reservoir: 3.2 oz / 90 g
    • Clean Water Reservoir: 5.2 oz / 147 g
    • Reservoir Tubing: 2.4 oz / 67 g
    • Storage Pouch: 0.7 oz / 20 g
  • Width (all components in pouch): 5-7/8 in / 14.9 cm
  • Length all components in pouch): 10 in / 25.4 cm
  • Flow (L / min): 1 liter / minute
  • Flow (Squeeze / min): 53 squeeze / minute
  • Cartridge Life: N/A

Review Context

In thru-hiking or expedition contexts, every calorie is precious. One of my least favorite ways to expend energy is filtering water, especially after hiking big-mileage days. As such, in testing this filter, I was looking for:

  • The efficiency of the Trail Filter component: time and energy expended per liter of water filtered
  • The efficiency of the Gravity Filter Component: time and energy expended per liter of water filtered

In addition to these factors, I was also examining:

  • The weight of the system: both as a whole and as individual components.
  • Portability and space taken up in the pack: Is the bulk of this system worth its performance, especially when considered next to the small amount of space used by a chemical treatment system?
  • Ease of use and intuitiveness of both components: In other words, is the gravity system easy enough that I will take the time to set it up after a long day of hiking versus just using the trail filter to clean my water?

Description of Field Testing

I tested the MSR Trail Base Water Filter system over the course of a multi-day backpacking trip in the Gila Wilderness of New Mexico. My water sources were primarily clear, fast-moving tributaries of the Gila River – important to note because still, cloudy, or tannin-laced water sources can significantly reduce the performance of any filter.

Cattle and stock animals are prevalent in portions of the watershed, as are large groups of campers and day hikers on the weekends. The higher-elevation areas of the watershed are far less frequently traveled, and parts of the Gila Wilderness are so remote that they receive almost no trail maintenance. As a result, the level of water contaminants probably varied greatly over the course of my trip.

During my test, temperatures were mild and did not dip below freezing overnight, another important factor in the performance of hollow fiber filters, as the sharp crystals that result from freezing can damage the fibers.

MSR trail base water filter kit 3
The MSR Trail Base Water Filter Kit spread out on a map of the Gila Wilderness.

Performance Assessment

My performance assessment of the MSR Trail Base Water Filter addresses the following items:

  • Efficiency of the trail filter component
  • Efficiency of the gravity filter component
  • Ease of use
  • Weight and size
  • Durability and construction

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