Review: MSR AutoFlow XL 10L

There's a dizzying array of water-purification products on the market these days. It seems like brands are in a contest to come up with the most far-fetched design—from trekking poles with built-in pump filters to batteries-required UV-light treatments, we're beyond the threshold of ridiculousness.

But one innovation has taken hold as a convenient solution to mass purification: gravity filtration. And for their part, MSR has drummed up the AutoFlow XL 10L Gravity Filter. After testing this product on several backpacking trips, it's become a mainstay in my multi-day backcountry kit.

The concept is simple: use the natural force of gravity to do the work of water filtration. This is a huge improvement over pump-style water filters, which are inefficient and tedious to operate. Ever try pumping water from a trickling alpine creek? Good luck.

With a gravity filter, all you need to do is get water into the bag, and the laws of nature will do the rest. It's as easy as watching an apple fall from a tree. And unlike chemical treatments, there's no residual flavor whatsoever—nor risk of running out.

The AutoFlow XL filters water at a rate of 1.75 liters per minute, and since the process is completely hands-off, you're free to carry about other tasks such as setting up camp, cooking, or just enjoying the scenery while the filter runs. Each filter cartridge has an average lifespan of 1500 liters (depending on water quality), and replacements can be purchased once the cartridge begins slowing down.

For additional storage capacity, I paired the AutoFlow XL with MSR's 6L DromLite Bag ($47), which holds plenty of water for a day or two in camp. The AutoFlow XL screws right onto the DromLite, which is conveniently threaded the same size as a standard Nalgene water bottle. The DromLite's cap also has a smaller inset cap for pouring water, and a tiny nozzle for hand washing.

The entire gravity-filter system and additional storage bag, combined, weigh only one pound.

Available at; $125.