LifeStraw Mission Gravity-Fed Water Purifier Review

Lifestraw Mission Gravity Water Purifier ReviewThe LifeStraw Mission is a gravity water purifier designed to filter and purify a large quantity of untreated water from natural water sources for base camping. Gravity-fed water filters and purifiers are more practical for processing large quantities of water than other backcountry water treatment systems such as boiling, pump-based system, ultra-violet light, or chemicals because gravity does the work for you with less physical effort and waiting than other methods.

The large Lifestraw Mission carries 12 liters of water when full and is very heavy
The large LifeStraw Mission carries 12 liters of water when full and is very heavy

The LifeStraw Mission is a modular system that includes a large and durable BPA-free polyurethane water bag, a pre-filter, hose, and a water-purifier. The water bag is used to hold untreated water and must be hung so that the force of gravity can force the water inside it through the pre-filter and purifier element which hangs below.

Available in a 5L and 12L, the water bag has a carry and hanging strap so you can hang it from a stout tree branch. The bag does get very heavy when you fill it, particularly the 12L size, and you might find it best to carry it part full and replenish it with a smaller container or cook pot as needed. While the bag has a roll-top, it’s not intended to transport water in a backpack and does not create a perfect seal when the top is rolled closed.

The Lifestraw Mission has an integrated pre-filter which strains out sediment and particulates before they can clog the purifier element

The Mission comes with a pre-filter that screws into the bottom of the water bag and filters sediment and larger particulates out of the water before it passes through the purifier. This is a crucial element missing from other “personal purifiers” like the Sawyer Mini and the Sawyer Point One where the flow slows noticeably over time, despite frequent back-flushing to eliminate sediment from gunking up the purifier element. I found the pre-filter quite useful for removing organic debris when scooping up pond water near the shore and purifying it, for instance.

The water hose clicks easily into the bottom of the water bag
The water hose clicks easily into the bottom of the water bag

Once you’ve filled the water bag and hung it up, you can insert the hose which connects the “dirty” water bag to the purifier element. The hose snaps into place when inserted into the bottom of the water bag and has a simple quick-release for use when you want to disassemble and pack the system. The hose remains attached to the purifier element although the two components can be replaced and reassembled as needed for cleaning or repair.

The Mission Purifier element has a red valve and blue valve on it and care must be taken not to confuse the two. The red valve is used to clear air from the hose to make the water flow faster through it. However, water that drains when the red valve is open is still “dirty” and un-purified. This valve should only be used when you first hang the system to prime it.

The red valve controls the flow of dirty water. The blue valve controls the flow of clean water
The red valve controls the flow of dirty water. The blue valve controls the flow of clean water which comes out of the blue hose attached to the side of the purifier.

The blue valve lets water flow through the purifier element and out a blue hose. This is “clean” water that has been purified. The purified flow rate through the blue hose is very slow, however, only purifying 1 liter every 6-9 minutes, making this solution best for basecamp solution, and less so for “real-time” use to resupply a group of hikers on the trail unless they were taking a long break.

The flow is also slow enough that you’re going to want a large catchment, like a big water jug, to capture and store the purifier water so you don’t have to stand around and wait for it to purifier multiple liters. I also suggest you bring a large funnel, because the water dribbles out of the blue “clean” hose, rather than streaming out, and it is hard to direct the dribbles into a bottle with a small opening.

The flow of water through the purifier is slow enough that you want to batch purifier a much larger amount of water in advance rather than waiting for it to flow through the purifier.
The flow of water through the purifier is slow enough that you want to batch purifier a much larger amount of water in advance rather than waiting for it to flow through the purifier.

You also need to be careful not to put the output hose into a clean bottle if it’s dirty. Called cross-contamination, it’s very easy to touch the blue output hose with hands that have been made wet by handling “dirty” water making anything that comes in contact with it “dirty” as well. If you then put the contaminated output hose into a water bottle that is only intended to hold “clean” purified water, you’re likely to contaminate its contents.

The Mission can also be back-flushed using the red squeeze bulb located at the bottom of the purifier element. After squeezing the bulb, open the red valve to let the purge water and trapped particulates drain.

Lifestraw Mission Water Purifier

Treatment Capacity
Ease of Use


The LifeStraw Mission Gravity Water Purifier is best used for as a multi-person base camp water purification solution to process large amounts of water from backcountry water sources. The inclusion of a pre-filter really sets this particular system apart and makes it easier to maintain over time.

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Microbiological Efficacy

The LifeStraw Mission is categorized as a water purifier by the Environmental Protection Agency and not a water filter because it is more effective at removing bacteria, protozoa, and viruses, including common contaminants such as Giardia, salmonella, Cryptosporidium, and E.coli. The purification element is a hollow fiber purifier with a .02 micron pore size guaranteed to purify 18,000 liters of water. Test results for the Mission purifier show that it removes 99.9999% of bacteria, 99.99% of protozoa, and 99.999% of viruses.

There is a real risk of cross-contamination if you insert the plastic outflow tube in a bottle to refill it
There is a real risk of cross-contamination if you insert a dirty plastic outflow tube into a clean bottle to refill it


Weighing 15 oz (dry,) the 12L LifeStraw Mission Gravity Water Purifier is best used as a multi-person base camp water purification solution to process large amounts of water from backcountry water sources. The notable inclusion of a pre-filter really sets this particular system apart from other gravity systems available today and makes the system easier to maintain over time.  While fully functional out of the box, you’ll probably want to bring along a collection reservoir to hold purified water that has run through the system since the Mission’s purification flow rate is somewhat slow.

Disclosure: LifeStraw donated a product for this review. 

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  1. How about a comparative analysis with the Kataydn Camp gravity fed water filter and others?

    • Here’s one with the Platypus Gravityworks filter. I think Grandpa has one, if he cares to chime in.
      Strengths: Faster flow rate. You can use the reservoirs to carry water.
      The rest will have to wait until car camping season.

      • I don’t have the Platy system. What I did was rig up a gravity feed on a Sawyer Mini. I got 5′ of vinyl hose, drilled a slightly smaller hole than the O.D. of the hose through a cap from a soft drink bottle and then forced the hose through the cap, which threads onto the end of the Sawyer bags. I heated up the other end so that I could force it onto the input end of the Mini filter. The Sawyer bags have holes so that a cord or ‘biner can be put through the back end. I hang the dirty bag (Sawyer bag) in a tree or in some other way suspend it 5′ or so higher than my clean water receptacle and let it run through the filter.

        I used that system a year ago when kayaking 5 days on the Rio Grande and it worked well but I also decided on some mods (which I forgot to do once I got home). I decided to find a clean receptacle that the end of the Sawyer Mini would fit into nicely to keep me from having to keep holding the Sawyer over my clean receptacle. I’ve got a couple 2L plastic jugs that would work for that but they are bulky for backpacking.

        Another flaw in my system is that vinyl hose gets REALLY stiff when cold and wants to coil up like a spring, adding to the futz factor when using. It also shrinks a bit, which makes it harder to fit over the input of the Mini. I ordered some silicone hose, which should be in here soon. I’ll see how that works when cold.

        The Sawyer system comes with a ½, 1, , and 2 L bag. I’ve heard they have a tendency to break open, although I haven’t experienced that. They only have one opening, which a soft drink bottle cap will fit. That opening, along with the fact the bag wants to stay flat, makes it hard to plunge it into a water source to fill. The bottom will fold out in such a way that an empty one will stand by itself so that you can fill it from another vessel.

        On my hike last month in the Chisos Mountains in Big Bend National Park, I sacrificed a plastic water bottle to be my vessel of choice to stick into the water pool in Boot Creek to use to fill the Sawyer bags, which took 7 full bottles to fill, plus the full dirty bottle for reserve. Coupled with my abortive attempt to fill the Sawyer bottle from the creek, that was 9 times I put my hand under water in an icy stream in early January. My hand was so cold, it was useless and the sun was about to set and I needed to put another couple miles behind me on the trail. With the arthritis I have, cold hands don’t function. I fumbled around with my good hand for a chemical heat pack, which I’ve never used before. I also decided not to try to filter there but just to load the dirty water bags into my pack and get back on the trail. Once I got my hands and heat pack back into the pogies on my Pacer Poles, the feeling slowly came back. I’m going to experiment soon at home with wearing a waterproof SealSkinz glove to see if I can handle repeated plunging into ice water.

        At camp, I first tried the squeeze method where I’d screw the Mini filter on the end of the dirty bag. After several minutes, I’d barely gotten enough filtered to make a cup of hot chocolate. I also had to squeeze so hard I was afraid I’d burst the bag and I didn’t want to get any wetter than I already was in the fog and icy drizzle. I broke out the 5′ vinyl hose and my rigged cap, hung the bag in a tree and was amazed at how fast it filtered. I sat down at the base of the operation with my cup of hot chocolate and topped off all my bottles. I had one other bottle I should have sacrificed to be a dirty bottle back at the creek. Had I done so, I’d have had just enough for the long hike the next day. Instead, I panhandled a liter off other hikers the following afternoon who were passing me on the way to the trailhead.

        When my silicone tubing arrives, I’m going to do more experimenting on perfecting my system. I’m going to also experiment with quick connects and a shut off valve.

        The Sawyer Mini filter can’t be frozen or it will ruin, however, it does fit into a Ziploc snack bag. I kept the snack bag in my pocket and sleeping bag to prevent it from freezing.

        • I use my cook pot when I need a water scoop. It has handles though.

        • My JetBoil doesn’t have very substantial handles. I think I’d still have frozen my hands. Some of my other cooking systems have handles that I could use. I’d planned on using a different one but couldn’t find it in my backpacking gear tub when I was in a hurry packing for the trail trying to beat a major winter weather system, which didn’t turn out to be as bad as advertised.

          Boot Spring was dry so I had to use pools in Boot Creek. They can get pretty grungy looking. When I scoop water that has green stuff in proximity to the surface, I turn the bottle upside down, plunge it deep past all the surface flora and fauna and then turn it upright to fill a few inches under water. There’s fewer “floaties” to filter and/or eat that way.

    • Stuart, I haven’t tried any other gravity filters, But I recently got a Katadyn Gravity Camp 6L and used it this past weekend. It is fast. And no pumping. It’s a winner in my book!

  2. I’ve been looking at this system for about two weeks now and you have just convinced me to buy it…. Thanks for a great review..

  3. Are replacement filters available? Any any of the tube based gravity filters can have a pre-filter or charcoal filter installed inline.

    • No replacements available except the pre-filters. I guess they think 18,000 is an effectively long product lifetime. Not sure what tube based filters you’re referring to. You can’t replace the filter element in a Platy Gravity Works or a Sawyer. You have to replace the entire filter unit.

      • Yes, the filter as a sealed unit is still a replacement filter separate from buying an entire new unit, hoses, bags and all.

      • The Sawyer, being a standard size, ought to be able to take scientific and industrial small scale pre-filters. A cheap glass wool pre-filter would be a good product for Sawyer.

  4. Very impressive filtration specs. Good to know what’s possible. Heavy though, almost a pound dry. But if you need it it’s great. Unlike Aquamira, it gets viruses too.

    Looks like this tech needs a long column to work well so I wonder how much smaller and lighter they can get. But if much lighter I’d use it solo. I like the no mix, gravity flow idea. Just fill at the last stream crossing before camping and let it work while setting up and overnight. I’ll wait for an ultralight model with those filtration specs though, even if life is much shorter.

  5. I have the Platy gravity works and really like it; would recommend it to anyone who wants a system like this. The flow rate is very fast for the 4L. Used this when I started distance hiking but steered towards the drops and gatorade bottle-less stuff to deal with-and changed my preference from drinking water from hydration bag. Best used with multiple people (kids) and do like it on the trail, vice just car camping (you do need a water scoop though). Do not use this filter inline…it doesn’t work well at all. The time I tried this I ended up squeezing the water into a bottle – the suck, literally sucked and no good way to backflow…if you want to squeeze water, just get the Sawyer squeeze or mini.

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