Do you need clean water for large groups of people? The MSR AutoFlow XL gravity filter stands out for its large capacity reservoir that filters 10-liters of water with minimal effort. The gravity filtration set-up requires you to collect water, hang the bladder, and wait. We tested this while guiding a large group of 20 students along the Gunnison River in clear and turbid water conditions. In both cases, this filtration system gave us the water we needed. While our most significant caveat is the amount of backflushing required to maintain a reasonable flow rate, we appreciate its relatively fast flow rate and packability. This is our favorite model for clean water at base camp or when traveling in groups.
MSR AutoFlow XL Review
Compare prices at 2 resellers Pros: Durable, easy to use, efficient, high volume
Cons: Requires regular maintenance, flow rate is sub-par, filter can't be frozen
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Our Analysis and Test Results
The AutoFlow XL gravity filtration system requires no hands-on work to filter 10L of water in one sitting. It's our favorite for basecamps, large groups, and whenever large quantities of water need to be filtered.
The AutoFlow XL is capable of removing all the critical biotic and particulate substances that you might find in your water.
The 0.2-micron hollow filter cartridge will rid your water of stinky substances, protozoa, and bacteria. We tested this while group camping on the Gunnison River that is ripe with high levels of sediment and contamination of protozoa and bacteria that could potentially make our group sick. Thankfully, like most places in North America, this gravity filter proves to perform flawlessly.
It's important to note that like all the filtration systems tested in this review, the pore size is not small enough nor ionically charged to remove viruses, heavy metals, pesticides or microplastics. So, if you plan on traveling to areas where this type of pollution is rich, this is not the filtration system for those trips. Though, anywhere in North America or where these pollutants are not typically found in water sources, it works well.
Durability and Maintenance
This gravity system offers a high level of durability with only a little bit of maintenance. The filter itself is one system, without any moving parts or complexities. This makes it less likely to fail in the field.
The bag is composed of a thicker plastic composite that seems resistant to punctures and tears. When filling up the full 10L, we were a little worried about the seams splitting, but the RF welding is super strong and reinforced enough to uphold the weight. On the underside of the bag is a 1000-denier flat base that allows you to set the bag down on rocky or spiky surfaces without worry. The filter itself is also quite durable and built to withstand falls from 7 feet high. Just be sure to avoid freezing, as the cartridge will be deemed unusable if it does freeze.
While on a group camping trip with 20 high school students, a few of the autoflow systems that we had on hand began to reduce the flow significantly. At first, we were a little concerned as this was our only way of water filtration. However, when we simply flipped the filter around on the tube to backflush the system, it started to run at the initial rate again. While they do recommend only a half-liter to flush the system, we'd recommend filling to the half volume of the bag (about 4 liters), then backflushing it with the full amount. It's also important to backflush after every significant use to ensure the filter stays clear….especially in turbid water. After we ensured this type of maintenance, our filtration system remained reliable and efficient. This filter works for about 1500L before it needs to be replaced, according to MSR.
We love this system because you just need to load up the bag, hang it high, then let it do its work. When measuring treatment time, we filtered a liter of water three times, then averaged how fast it took to make one liter of water. In the field, we wouldn't really think about this much, as we'd set it up in the morning and walk away. By the time hiking time came, we'd fill up and be on our way.
Depending on the clarity of the water, treatment time does change. With normal tap water, we measured one liter to take about 2 minutes. This would vary with how full the bag was. The more full the bag, the faster the flow. As the bag emptied, the flow rate began to decrease. Also, when more sediment was in the water, the flow rate decreased to about twice the time and required many backflushes. This was a pain when trying to filter 10 liters.
But since we had time in a group setting, we typically just walked away and had a reservoir of clean water waiting for use when we came back to check it. In general, this is one of the slowest treatment times we observed between all the gravity filters and other filtration systems. However, when testing it for use in a group setting, where time wasn't of the essence, it worked perfectly.
Weight and Packability
The components of the system are all stored in a convenient bag that takes up very little room in a backpacking backpack. From the point of view of a backcountry guide, who typically carries more backup gear for a group, this system proves to be very convenient. It packs easily into cracks and crevices, while the weight is minimal. The bag rolls up, with the receiving reservoir either being a water bag that you might bring along a water bottle, or a dromedary. All in all, it's lightweight and packable.
Ease of Setup
Set-up on the system is easy peasy. To collect water, the reservoir has a roll-top architecture that requires you to get to a water source and either plunge it into the water or hold it across running water. The downside of such a huge bag is that it's really difficult to collect from shallow and stagnant water sources. Tall banks require you to hover over them to try and reach the water.
Once the water is collected, simply roll the top down and clip it onto a very sturdy surface. A 10-liter reservoir filled with water weighs about 22 lbs! It's important that you find a surface that can support it. We also tried placing it on a sloping hill. This works too, but the flow rate decreased dramatically.
From here, clip in the tube, attach the filter in the correct orientation (as per the picture), then connect your receiving reservoir. The set comes with an attachment for a standard wide-mouth (think Nalgene!) bottle.
While we appreciate this attachment, we learned that it must be used when the bottle is upright. The attachment can't be screwed on completely as oxygen can't be vented, and thus the water doesn't flow through the filter. Another favorite that we like to filter into is our MSR Dromedary that has the option for a tube plug-in attachment. Overall, set-up is more cumbersome than other, simpler setups, but pretty easy for a system that filters 10 liters of water at once!
Ease of Filtration
This is a gravity filter! Once the system is set-up, all you need to do is sit back and relax. If you attach a dromedary or reservoir that is less than 10L in size, the system will stop filtering if the system is closed. In addition, if you want to stop the filtration process, simply use the hose clamp to do so.
The quality and lightweight characteristics of this system make it well worth the value. For the price, you'll be buying a gravity filter that is easy to use, practical, and durable. With a 1500L filtration capacity, you're looking at about 150 uses for ten people.
The MSR AutoFlow XL is a 10L gravity filtration system that is renowned for its easy set-up and large capacity. While it does require regular backflushing, especially in turbid water, it's the perfect filter for large groups or guided use. Just be sure that you can hang it in a place that can take the weight of 22lbs of water. This notable mention is our recommendation if you're seeking a system that can make a lot of water for a large group of people.
— Amber King