Hands-on Gear Review

LifeStraw Flex Review

LifeStraw Flex
Top Pick Award
Price:  $35 List | $34.95 at REI
Compare prices at 2 resellers
Pros:  Lightweight, fast, compact, can be used in different configurations, inexpensive
Cons:  Some leaking between bottle and filter
Bottom line:  The Flex wins our Top Pick Award for trail running and on-the-go uses.
Editors' Rating:   
  • 1
  • 2
  • 3
  • 4
  • 5
Weight (including bag and all things that would be carried) (ounces):  4.4 oz
Effective Against:  Protozoa, bacteria
Time to Treat a Liter (Timed Test):  Drink through straw, fairly instant, 2:57 min filling 1 liter
Manufacturer:   Vestergaard

Our Verdict

The Lifestraw Flex beat out the Katadyn BeFree this year as a versatile, lightweight trail running and backpacking option. It takes our Top Pick Award for this reason. It is an excellent choice when you don't want to carry water but instead drink it on the fly and are near a water source. The Flex can be screwed on to disposable small mouthed bottles and used in line on a hydration bladder, making it more versatile than the BeFree (and we're hoping it is more durable as well). It is small enough to fit in a pack or pocket and able to be pulled out when you need it. Its small, 20 ounce soft sided bottle is not great for treating large quantities of water, and so we do not recommend doing so in group settings.


RELATED REVIEW: Best Backpacking Water Filters and Treatment of 2018


Our Analysis and Test Results

Review by:
Jessica Haist

Last Updated:
Monday
May 21, 2018

Share:
The Lifestraw Flex is an excellent choice for an on-the-go water filter that is compact and light. This product wins our Top Pick Award for the best trail running option or days out along the water. Throw it in your pack, vest, or pocket for your long trail runs or hikes to have drinking water instantly from the source without having to carry it. When comparing the two, we think this is a slightly more durable product than its competitor, the Katadyn BeFree.

Performance Comparison


The Lifestraw Flex is great for day hikes when you'll be near water.
The Lifestraw Flex is great for day hikes when you'll be near water.

Reliability/Effectiveness


If you're spending your time hiking and running the beautiful trails of the US or Canada, the Flex will be your reliable companion.


The Flex will filter out all harmful bacteria and protozoa you'll find in the US or Canada. If you are traveling to countries abroad and are concerned about viruses contaminating the drinking water, you'll want to invest in a model that treats viruses. The lightest virus fighters in this review are the Aquamira Frontier and the Aquamira Water Treatment Drops and are decent choices for trekking in the wilderness when abroad.

The Lifestraw Flex is a lightweight and easy to use option for day trips.
The Lifestraw Flex is a lightweight and easy to use option for day trips.

One of our concerns with the Flex is in the durability of its bottle as it is very similar to the Katadyn BeFree. In the past, the BeFree bottle ripped and had a hole in it during both times we tested. Fortunately for the Flex, its durability seems of greater quality than the BeFree; this is based on the fact that we've used it more than the BeFree and it has not sprung a leak yet, although it does have the same bottle collar attachment as the BeFree's 20oz bottle (in which the hard plastic meets the soft, which tore open after a few uses). Another concern we have with the Flex is that the coupling between the filter and the included bottle is not incredibly tight; when we squeeze hard, it starts to leak, which could result in contaminated water dripping into our filtered water container.

You can still use the Flex as a straw style filter  but it is short and difficult to get down to.
You can still use the Flex as a straw style filter, but it is short and difficult to get down to.

The silver lining to these concerns, and why we prefer this product to the BeFree, is that this unit is much more versatile. The Flex can be screwed on to a small-mouthed bottle or be used as an original Lifestraw unit drinking directly from the source. As a result, if the included bottle fails, there are still two ways to use the filter in a pinch! It can also be used in line with your hydration bladder, but we found it difficult to suck water through in this set-up (but not impossible).

Ease of Use


The Flex is easy to use. You simply fill the included bottle, screw in the unit, and squeeze or drink through the nozzle.


It can get tricky filling the bottle from a shallow source, and we prefer a hand pump like the Katadyn Hiker Pro or the MSR Trail Shot, as they have hoses which reach into hard-to-reach places.

You can also use it at the end of your hydration hose  but we found it difficult to get any water through.
You can also use it at the end of your hydration hose, but we found it difficult to get any water through.

As we mentioned, we found it very difficult to suck water through the filter unit attached to a hydration bladder hose. We wouldn't recommend it in most scenarios, though it will work in a pinch.

The Flex is easy to assemble  just fill the bottle and screw on the filter!
The Flex is easy to assemble, just fill the bottle and screw on the filter!

Weight


The Flex is a great, lightweight little unit, weighing in at 4.4 ounces. It's slightly heavier than the BeFree and Sawyer Mini models.


We suspect this has to do with the carbon unit in this filter meant to improve the taste of your drinking water. Neither the BeFree or the Mini have any carbon. You can remove the carbon component to make the filter even lighter.

The Lifestraw and Aquamira Frontier filter units
The Lifestraw and Aquamira Frontier filter units

Treatment Capacity


The Flex's filter is good up to a claimed 1850 liters or 500 gallons. This puts it close to the TrailShot's 200 liters but nowhere close to the Mini's 100,000 gallons. Eighteen hundred and fifty liters is still a lot of water and will last several seasons of backcountry use.


The Flex comes with a 20-ounce bottle, which made it difficult to filter large quantities of water at a fast pace. It's best utilized for one person on a backpacking or day trip. The BeFree's three-liter bottle solves the problem of being able to filter large quantities of water, and we hope that Lifestraw will come out with a larger volume container for the Flex.

The Lifestraw Flex's bottle is 20oz capacity  so not great to treat a large quantity of water.
The Lifestraw Flex's bottle is 20oz capacity, so not great to treat a large quantity of water.

Speed


The bonus of a filter like the Flex is that it produces drinking water in the time it takes to dip your bottle in the water, and screw on the top. This equates to an experience that is almost instant. If you're trying to fill up water bottles, you'll experience a longer filter time. It took us almost three minutes to fill up a liter since we had to refill the small bottle multiple times.


Best Application


The Flex is a great choice for trail runs and long day adventures where you'll be on or near water. Trail running, boating, or day hikes are great situations to bring the Flex to. Instead of carting around liters of water, you can dip this bottle into the source when you want a drink and continue on your merry way. The Flex could be a backup filter for longer backpacking trips, though ultimately, we would recommend bringing something more reliable with a larger capacity, like the Platypus GravityWorks.

The soft sided bottle has a pretty wide opening that is easy to fill.
The soft sided bottle has a pretty wide opening that is easy to fill.

Value


Retailing for $35, the Flex is a great value! It is $5 cheaper than the 20oz BeFree model, and we hope that overall, it proves to be more durable. It is undoubtedly more versatile than the BeFree, and it can be used on different small mouthed bottles or in line with your hydration bladder hose (although not recommended). It also has the bonus of a carbon filter component to help with the taste and odor of your water which the Mini and BeFree don't have. The original Lifestraw retails for a jaw-droppingly low price of $20; if you're looking for a cheap back up and are interested in drinking directly from the source, we recommend the original Lifestraw.

Conclusion


The Lifestraw Flex earns our Top Pick Award this go around, as it's the best option for a lightweight, on-the-go filter. It excels for trail running or fastpacking and can fit in your pocket, vest, or pack easily without weighing you down. We're taking a chance in hoping it's more durable than the Katadyn BeFree that previously held this award. The Flex is a versatile choice that can be used on different bottles and retails for a great price!

Attaching the Flex's filter to a hydration hose. It feels like this may fall off if you let it dangle.
Attaching the Flex's filter to a hydration hose. It feels like this may fall off if you let it dangle.
Jessica Haist

You Might Also Like

OutdoorGearLab Member Reviews


Most recent review: May 21, 2018
Summary of All Ratings

OutdoorGearLab Editors' Rating:  
  • 1
  • 2
  • 3
  • 4
  • 5
 (5.0)
Average Customer Rating:  
 (0.0)
Rating Distribution
1 Total Ratings
5 star: 100%  (1)
4 star: 0%  (0)
3 star: 0%  (0)
2 star: 0%  (0)
1 star: 0%  (0)


Have you used this product?
Don't hold back. Share your viewpoint by posting a review with your thoughts...