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Lifestraw Flex Water Filter Review

Lifestraw Flex Water Filter Review

The Lifestraw Flex is a screw-on style backcountry water filter that is compatible with a wide range of soda-sized water bottles and reservoirs. While it comes with its own 22 oz soft-bottle, you can also screw it onto standard-sized soda bottles, Platypus or Evernew reservoirs, integrate it into a hose-based hydration system, use it in a gravity filter configuration, or even as a hand-held filter to drink directly out of a stream if you don’t mind crawling on your belly to do it.

Lifestraw Flex Water Filter

Treatment Capacity
Ease of Use

Lightweight, Fast, and Effective

The Flex is a two-stage backcountry water filter that filters out bacteria and parasites, with an optional activated carbon capsule that reduces chlorine, odors, organic chemical matter and bad tastes. It can be used with the included soft bottle, common soda bottles, inline, or with other reservoirs in a gravity-filter configuration. The flow is fast and the filter is easy to clean.

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Specs at a Glance:

  • 0.2 micron pore size
  • Includes large syringe for backflushing
  • Removes 99.999999 % of bacteria
  • Removes 99.999 % of parasites
  • Reduces organic chemical matter (pesticides, herbicides, VOCs)
  • Exceeds NSF 53 standard for reduction of lead and other heavy metals
  • Exceeds NSF 42 standard for chlorine reduction
  • Exceeds US EPA drinking water standards for bacteria and parasites
  • Microbiological filter lasts up to 2,000 liters / 500 gallons
  • Replaceable carbon capsule lasts up to 100 liters / 25 gallons
  • Microbiological (Blue) Filter weight: 2.0 oz
  • Carbon capsule weight: 0.3 oz
  • Soft Bottle weight: 1.0 oz
  • Removes 99.999% of microplastics
  • Do not freeze as this will break the filter element

The Flex is a two-stage filter, a microbiological hollow fiber filter (blue) that filters out bacteria and parasites, with an optional activated carbon capsule that reduces chlorine, odors, organic chemical matter, and bad tastes.

The microbiological filter has a 500 gallon lifetime while the carbon capsule only lasts 25 gallons, necessitating frequent replacement if you use the two together frequently. The replacement capsules cost $10 per pair.

But you don’t have to use an activated carbon capsule if you don’t want to. It can be removed from the cap and the unit reassembled without it. While the taste of natural water sources doesn’t bother me, I can see the benefit of using the carbon capsule to remove additional contaminants or odors, especially if you drink water from sources near agricultural activity where herbicides and pesticides are used.

The Lifestraw Flex consists of a soft bottle, a blue microbiological filter, a grey cap, and an activate carbon capsule, shown inserted into the cap.
The Lifestraw Flex consists of a soft bottle, a blue microbiological filter, a grey cap, and an activate carbon capsule, shown inserted into the cap. A plastic backflush syringe is also included (not shown)

The Flex also includes a 22 oz soft bottle. It can be combined in a number of different ways with the other components of the system depending on your needs. If you just want to use it as a bottle and not a filter, you can screw the grey pour top onto it as a cap. If you want to add in the blue microbiological filter, it screws into the interior of the pour spot, which then screws onto the soft bottle. And so on, like a Russian nesting doll.

While you can fill the Flex bottle from a stream and filter water, the real utility of this product is its ability to interoperate with other bottles and containers. For instance, you can screw the filter element onto the top of a soda bottle, or a higher capacity Platypus or Evernew soft bottle, or plug it inline with a hydration system. My preferred configuration is to use the Flex filter with a Platypus reservoir to squeeze filtered into a separate SmartWater bottle.

The one weakness of the Flex system is the system’s flow rate, which is comparable to a Sawyer Mini, but slower than the large Sawyer filter included with the Sawyer Squeeze System. It’s also slower than the Katadyn BeFree water filter.

The advantage of using the Lifestraw Flex over the Katadyn BeFree, is its compatibility with soda bottles, Platypus/Evernew reservoirs, and the ability to mate it with hoses in an inline or gravity filter setup. The Katadyn BeFree Filter is only compatible with Katadyn or Hydrapack soft bottles, which is a pretty limited universe.

The Lifestraw Flex is compatible with a wide range of bottle and reservoir types
The Lifestraw Flex is compatible with a wide range of bottle and reservoir types

The format and compatibility of the Lifestraw Flex remind me of the AquaMira Frontier Pro Filter (see review), which is also compatible with regular soda bottle sizes, Platypus/Evernew Reservoirs, and can be used as an inline or gravity filter when connected to hoses. The Frontier Pro, however, has a limited 50 gallon lifespan. The only other filter that can be used on all of these configurations is the Sawyer Mini, which is rated for 100,000 gallons (probably exaggerated), but has a pore size that’s 0.1 micron compared to the Flex’s 0.2 (microns).

Net-net, if you want a water filter that is widely deployable in different configurations and reduces chlorine, odors, organic chemical matter, and bad tastes, then the Lifestraw Flex with its activated carbon capsule is really the best alternative compared to the Sawyer Mini, Squeeze, Katadyn BeFree, and AquaMira Filters.

  • If you don’t need an activated carbon filter, but you do want the ability to support a wide range of bottle types and hose-based configurations, the Sawyer Mini is probably the best choice because it has a longer lifespan than the Flex and a smaller pore size.
  • If filtering speed is your biggest priority, I’d opt for the Katadyn Befree 3.0L water filter, which is the fastest option.
  • If speed and bottle/reservoir compatibility are your most important needs, then I’d recommend the Sawyer Squeeze.

Disclosure: The author purchased this product with his own funds.

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  1. Yes the Life-straw Flex can be used in more ways but would i recommend it over the KATADYN Be-Free NO because the thing with water is that you need lots & lots of it

    Besides for drinking you need clean water for cooking, watering your garden, cleaning purposes (disenfection), bathing, laundry

    And in a diaster if you only had the lifestraw flex you would barely have enough for drinking yet alone your other needs why because it filters to slow like sawyer slow while KATADYN have outstanding flow flow rates for almost all its products

    Also if you buy 2 3L or 4L replacement hydrapaks that would last you for the duration of your diaster even if it was a couple years because they are so durable as long as you take care of it and just don’t go throwing it down on rocks and slinging it around it will last a really long time

    • But the Lifestraw is compatible with all soda and pop bottles. They’re free once used. You can reuse them and there will be plenty of them “floating” around after your disaster. That’s not the case with hydrapack bottles which have a proprietary size and require a proprietary size bottle, not a standard.

    • If you are able to boil your water, you have solved every filtering problems. Cooking, if water is boiled, does not really need filtering.

      So it’s use is mainly important for drinking on the go and gaining fast way to drink water. I own BeFree, Sawyer Mini and Flex. Both have their pros and cons.

      I would say Sawyer wins in capacity, size and better filtering. Flex filtering volume is lower than Sawyers and Sawyers filtering is better, but the mechanism ans utility is quite par. I use these attached in my HydraPak water reservoir.

      BeFree lacks utility, becuse it is pound to its own bottleline, HydraPak. Impossible to attach to any other bottle, or reservoir is a big con.

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