MSR AutoFlow XL Review

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.

Performance Comparison

Water Quality

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. However, 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.

Treatment Time

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 Set Up

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, as the 10-liter reservoir filled with water weighs about 22 lbs. You can also place the filter on a sloping hill, though the flow rate decreased dramatically. From here, clip in the tube, attach the filter in the correct orientation (as per the picture), and 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 since 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 DromLite Bag, which has the option for a tube plug-in attachment. Overall, the setup is more cumbersome than other, simpler setups, but pretty easy for a system that filters 10 liters of water at once!

Ease of Filtration

Since this is a gravity filter, the only thing you need to do is set up the system by filling the reservoir and hanging it so that gravity can do the work.

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.

Should You Buy the MSR AutoFlow XL?

The quality and lightweight characteristics of the AutoFlow XL make this system well worth the price tag. The gravity-fed system produces high-quality filtered water, is highly durable, and is very easy to use. The Autoflow XL is also super practical, especially if you're looking to hydrate a larger group for an extended trip into the backcountry. The 1,500-liter capacity translates to about 150 uses for a group of ten people. If you're considering the best option for group filtration, this gravity system should be at the top of your list.

What Other Backpacking Water Filters Should You Consider?

The MSR AutoFlow XL is a 10L gravity filtration system that is renowned for its easy setup and large capacity. While it does require regular backflushing, especially in turbid water, it's the perfect filter for large groups or guided use. If you're interested in another gravity system in a similar price range that would be great for a smaller group, like a family of four, check out the Katadyn Gravity BeFree 6L. This system requires less maintenance and offers the same ease of filtration with a little less capacity. And if you're looking for a gravity system that is more affordable, check out the LifeStraw Peak Gravity 3L. This filter has one-third less capacity but remains durable and easy to use.