The 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 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 Mission comes with a pre-filter that screws into in 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.
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 blue valve lets water flow through the purifier element and out a blue hose. This is “clean” water which 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.
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.
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.
Weighing 15 oz (dry,) the 12L 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 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 provided Philip Werner (SectionHiker.com) with a Mission Water Filter for this review.Editor's note: If you’re thinking about buying gear that we’ve reviewed or recommend on SectionHiker, you can help support us in the process. Just click on any of the seller links above, and if you make a purchase, we may (but not always) receive a small percentage of the transaction. The cost of the product is the same to you but this helps us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides. Thanks and we appreciate your support!