Indefinitely Wild

The MSR Trailshot Is Only Water Filter You Need

The $50 tool will save you from the runs caused by bacteria, protozoa, or particulates found in U.S. backcountry water sources

Ideal for fast-and-light adventures, you can drink directly from the Trailshot in lieu of filling a water bottle or bladder. (Photo: MSR)

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Am I right? They’re heavy, slow, expensive, and frustrating to use. Worse: The marketing around them obfuscates what they’re genuinely capable of, making it difficult to know which one can genuinely keep you safe.

Well, I think I’ve got an answer to all those problems. MSR’s new Trailshot weighs just five ounces, is slim enough to fit in your pants pocket, and removes absolutely everything that might make you sick, at least here at home.

What Is It?

It’s a tiny squeeze-to-pump water filter that removes nasty stuff with hollow fibers. Pores in those fibers are simply too small for bacteria, protozoa, or particulates (read: dirt) to pass through.

The Trailshot does not remove viruses, as do more expensive, heavier MSR filters, like the Guardian. I rank that as a good thing. You’re extremely unlikely to encounter problematic viruses in backcountry water sources here in the U.S., and going without the ability to remove them is a big part of what keeps the Trailshot so small, light, and cheap. This thing retails for just $50.

(Think a water bottle with a built-in UV light might be more convenient? Read this article first.) 

The Trailshot couldn't be simpler: it's just a filter cartridge housed in a rubber body that you pump to use, plus a rubber hose that you drop into the water source. (Photo: MSR)

Who’s It For?

MSR markets the Trailshot to trailrunners, ultralight backpackers, and other people who need to prioritize weight and packability over all else. While it is ideal for those applications, I think that’s mostly to avoid putting this more affordable filter in direct competition with the brand’s other offerings.

The Trailshot is just so damn convenient that it’s hands down the best water filtration option there is right now. Period. It flows fast enough (one liter a minute) to fill the bottles of a small group, while remaining so light and small that it makes sense to carry one even if you don’t think you’ll need a filter.

Really, the only reason to buy something else is if you’re traveling to a country where viruses, chemicals, or toxins in the water are a concern, or if you need multi-year longevity.


The Trailshot couldn’t be simpler. The filter is housed inside a rubber body that you squeeze to suck water through. There’s a 12-inch long tube fitted with a metal screen that you dangle in the water source, giving you plenty of room to fill an upright water bottle, or to drink directly from the spigot.

Clog the filter in dirty water? Just shake it vigorously to remove the impediment. There are no tools required, and you can’t disassemble this filter. That means there’s nothing to fail in the field, and no parts to lose. Like all other MSR filters, the Trailshot has a positive end-of-life indicator: the filter slowly clogs over time, and will stop passing water when it’s unable to clean it. Filters with positive end-of-life indicators will never allow you to drink dirty water.

Using It

I’ve been carrying one of these for a little over a year, and it’s been the only filter I’ve used in all that time.

Using it doesn’t require instructions or demonstration. I’ve simply handed it off to neophyte campers, told them to fill their water bottles, and they’ve come back with full containers a couple minutes later. In the past, doing that with more complicated designs has resulted in broken handles and lost parts.

Next week, over the Thanksgiving holiday, I’m taking five or six friends on a tough backpacking trip. We need to keep our packs as light as possible, but we’ll also be drinking from stagnant, algae-filled pools, sulfur hot springs, and from a stream filled with bighorn sheep poo. The Trailshot is the only filter we plan to carry, and it’ll deliver clean, nice-tasting water for everyone throughout the trip. I know that because I’ve carried it there before. 

In that year or so of frequent use, I haven't yet noticed a decrease in the Trailshot's flow-rate. At $50, that's amazing value. And it's also great that you can save a few bucks by replacing the filter cartridge with a $35 new one, without buying an entirely new Trailshot. 

With the spout removed, you can see the porous fiber filter cartridge. The metal screen on the end of the tube helps pre-filter larger particulates, extending the life of the filter. In over a year of use, the only part I've ever needed to clean was that metal sieve, and then that was just a case of rinsing it off. (Photo: MSR)


  • Small enough to fit in the pocket of your shirt or pants.
  • Flows as fast as larger pump handle filters.
  • No moving parts to break.
  • Service-free.
  • At five ounces, there’s no reason not to bring one along.
  • One of the cheapest water treatment options out there.


  • Sometimes it’d be nice to have a longer source tube for reaching those difficult water holes you find in the desert Southwest. But, it’d be easy to add a piece of your own tubing to do just that.

Should You Buy One?

Yes. The Trailshot will save you weight, space and money, while also saving you from the runs.

Buy Now

Filed To: Water TreatmentIndefinitely Wild
Lead Photo: MSR
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