LifeStraw Flex

A water purifier, in 2019? But I’m not heading to Timbuktu?!

Despite the availability of safe water in developed countries, when travelling in the mountains or away from urbanised areas, sourcing clean, safe water can be a challenge. Take earlier this year, I was supporting a friend on his Heart of Snowdonia Challenge, running with my camera and therefore, I decided to leave a bottle in the car due to space limitations. I followed the well-known rules

  1. Avoid stagnant water
  2. Make sure there is a constant strong flow
  3. Don’t drink downstream in case of contamination
  4. And so on…..

I played it safe for the most part, used due diligence and on the day, felt pretty sweet. However, that night, my body purged itself. You have no idea how happy I was to be back home, as the night before, I was sleeping in the back of my car, on a lay by just off the side of the A498. Things could have been much worse.

Of course, you can boil water, treat with iodine and/or chlorine, but, a system that takes away faff, waiting and steps, is a much simpler system for running and therefore, racing. I reached out to Spring PR with my dilemma and they sent me LifeStraw’s Flex filter to test in the mountains.lifestraw review 3LifeStraw’s Flex combines a lightweight filter with a soft flask, providing a system many a trail and ultra-runner would recognise from a distance and in principle. Furthermore, for wide mouth soft flasks, the filter can be screwed in (let’s call it retro fit for those who love that word) which opens up a whole world of further possibilities.

Let’s get the flask element out the way. It’s a 650ml soft flasks, which is a kin to any other on the market. My opinion, if you have a wide mouthed soft flask or bottle, which comes with your chosen hydration vest or belt, use it. If say you are using a Salomon S/LAB vest, which is designed for 500ml soft flasks, you will get a much better fit and allow you to integrate the system, if you use the 500ml flasks, rather than LifeStraw’s own.

Right. Science time. Well sort of.

Let it be known, clear as day, I am not a scientist, I got an A in Chemistry at GCSE and I have no idea how…. It’s the only exam I felt like crying after walking out. Anyway, normal service is resumed below.

LifeStraw claim that the Flex filter will remove;

  • 999999% of bacteria (E. coli)
  • 999% of parasites (Giardia, Cryptosporidium, etc.)
  • 999% of microplastics
  • Lead and other heavy metals
  • Chlorine
  • Bad odor and taste
  • Organic chemical matter

These are pretty big and bold claims. This is facilitated by 2 separate filters, a microbiological and an activated carbon, carrying out separate roles. The hollow fibre membrane removes the bacteria, parasites and microplastics, while the carbon filter removes the heavy metals, chlorine and organic chemical matter.lifestraw review 1Both are replaceable, with a lifespan of 2000 litres for the microbiological, which should become apparent with water no longer passing through, due to pores clogging. lifestraw review 5The carbon filter lasts for 100 litres and is recommended to be changed (on average), every 3 months. Ultimately, replacing the filters will be determined by how often and where you use the Lifestraw Flex.lifestraw review 4BPA free (ie safe to drink from) and recyclable, it’s a product designed to be disposed off when the time eventually comes and is food safe.

So, it’s got some mad tech involved, in a small, light package, but how does it perform?

First off, it comes with a syringe, to flush the filters before use. Make sure you follow the easy to follow instructions, before you head for the mountains.

I used the Flex at the Original Mountain Marathon/OMM and on training runs. The OMM was a great place to test, with no check points with water, a self-sufficient race, being able to source water where I could find it and consume, safe in the knowledge my internals aren’t going to get attacked, I and my running partner and tent accomplice for the night, could sleep easy.


I did find the end cap, which covers the hollow fibre filters came off a few times in use, so making sure you tighten it appropriately is key. The flow rate isn’t bad, but don’t think of it the same as a standard soft flask with a bite valve, you aren’t going to empty the soft flask in seconds. It does require you to work for your water, with a bit of a suck and a squeeze at the other end. Come on, your mind chuckling away whilst you read that, says more about you than me.lifestraw review 2The nipple, has a cap to cover it and prevents foreign bodies entering. If you can, keep these stored vertically when the flask has water in it. I found, using it in running belt, stored horizontally, water would escape and leave me with a wet back.

But should you go out and buy one?

As your primary water source when racing, I would advise sticking to a regular soft flask. As a backup or required filter, for an ultra in baron landscapes, yes, I would recommend it to be in your pack for when the time comes. If I was to go for a hike, I would happily carry it, as I’m not looking to hydrate as efficiently as possible , in the shortest possible time and I’m not going to be flinging the flask around repeatedly for hours. That and more often then not, there will be aid stations with safe drinking water.

Construction is strong, it’s well made and has survived multiple outings.

You may not require the LifeStraw for every day life, however, when the time comes for real adventure, its a strong contender for keeping your water clean, when there’s no other option to drink from sources, that at best would be described as “questionable” when it comes to safety.


Supplied by Spring PR | This is not a paid promotion

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