Dissecting a Life Straw : What is in this thing anyway?

Two Cautions for Water Filters

Have you ever wondered how a LifeStraw water filter works?  

Me too, so I did some research.  A lot of research, actually and I found some surprising information that, if ignored, could potentially impact your health.  (if you use membrane style water filters).  

This article covers two very specific limitations identified by the manufacturer, which are impact resiliency and freezing temperatures.  Simply put, Life Straws are effective and cheap, but there are serious limitations that need to be considered.  Avoid dropping your filter and don’t ever let it freeze, or the device could be compromised, and the water quality will be in question. 

Let’s take a quick overview of how membrane filters work and then explore the two cautions every user needs to know about, no matter if it’s a LifeStraw or any other membrane water filter on the market. 

Photo credit: www.lifestraw.com

The LifeStraw (like many others) uses membranes to filter water.  It’s a simple process where the user puts one end of the straw into dirty water and then sips clean water from the mouthpiece on the opposite end.  When the user creates a vacuum inside of the straw, dirty water is drawn up and into the hollow fibers of the membranes to be filtered.  The pores of the membranes are small enough to trap contaminates, but large enough to let clean water pass through.  

These water filters are economical, easy, and convenient. However, that doesn’t always mean they are the best option.  It’s important to note that these water filters were originally designed in 2005 to be used as emergency response tools when responding to natural disasters.  They weren’t designed as a long-term sustainment option.  Although, uses change as devices become more mainstream.  

Photo credit: www.lifestraw.com

I was intrigued by two specific notes in the owner’s manual, with the first referencing the durability of the water filter straw.  The manufacture gave the following caution: 

Interesting.  Now I don’t plan to utilize my LifeStraw as a hammer or pry bar, but if I happen to have it in my pack, which falls down a hill, or gets tossed out of a vehicle…or pick any number of plausible scenarios, will my LifeStraw still give me safe drinking water?  I’m not so sure anymore.  

Either that caution is a huge liability clause or the device really is more fragile that I originally considered.  And that’s OK, if these limitations are respected and understood.  

The second item that jumped out (and was the catalyst for a real-world test) were the instructions not to let the LifeStraw freeze.  

This is a big limitation that users of membrane style water filters need to know about.  If moisture is inside of the filter when the temperatures drop below freezing, the membranes can very likely be damaged.  And the thing is, you wouldn’t necessarily be able to tell without laboratory testing.   

I wanted to see for myself what would happen to the membranes if the water filter froze, so I came up with a realistic scenario.  Drink from the filter, blow it out and then drop it in a ruck that would be left outside in freezing conditions for the entire night.  Then, cut it open and see what happened to the membranes.  

LifeStraw Inlet (pre-filter removed) 

(photo credit: Jessie Blaine, American Partisan)

Recently, I was able to finally run the test and the temperature bottomed out at 27 deg Fahrenheit.  The sub-freezing conditions didn’t last long as the temperature was below 32 degrees F for about 6 hours.    This was a light freeze, but it was realistic for this area of the country.   

The next morning, I brought the filter inside and let it warm up to room temperature.  The first test was to see if the straw was still usable, and it was.  I could drink water through the straw with no noticeable changes.   

Then second segment of the test was to take apart the filter and see if there was any visible damage to the membranes. These filters aren’t designed to be disassembled, so I had to be careful not to damage the membranes during the process.  

The inlet strainer and the outlet mouthpiece were affixed to the straw housing, but they came off with relative ease.  I simply placed the ends of the straw against the edge of a table and with a quick downward press, the ends popped off.  With the ends off, the internal membranes were exposed.  And that was it…an inlet strainer, a membrane bundle, a mouthpiece, and a housing to hold it all together.

Here are a few observations.  

The shell.  The shell of the straw had structural integrity but was surprisingly brittle.  I made a few cuts with diagonal cutters and then started prying apart the housing with my fingers.  I was surprised at how easily the shell just seemed to crack and crumble.  After taking this apart, I understand why they issued a warning.  

LifeStraw Shell and Membrane Bundle

(photo credit: Jessie Blaine, American Partisan) 

The membranes.  They were all intact, even after being exposed to minor freezing. None of the membranes had any external damage that was visible with the human eye.  Like other types of membranes, the ones inside this filter are not very durable.  When I pulled on them, they broke with very little force.  Remember, membranes are super thin, hollow fibers designed to separate components on a microscopic level, they aren’t designed for structural strength.  I could see how a deep freeze of a wet filter could cause some concern and I also understand how a hard impact could compromise of the membranes. 

LifeStraw membranes

(photo credit: Jessie Blaine, American Partisan) 

In summary, these are great water filters and have been used by thousands of backpackers, outdoorsman and relief workers all across the globe.  Membrane filters are cheap, lightweight and effective.  But, like any other piece of equipment, the limitations have to be respected.

No drops and no freezing.   

I own, use and rely on a variety of different water filters and the membrane style filters have a place in my preparedness plan.  Knowing the limitations is the key to proper use.  These might not be ideal in all situations, but they work for me.  My key criteria are satisfied: simple, easy to use, economical, effective and efficient.  

Are they perfect? 

No. 

Do I recommend them?

You bet I do!

-Jessie

Jessie Blaine is a former Marine living in refuge somewhere in the Lone Star state.  He is in a perpetual state of learning, which is the second-best state to be in, with the Lone Star state being the first.