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Best Overall: MSR Guardian Purifier Pumps at Amazon "The pump-styler filter is fast...and self-cleans with every pump."
Runner-Up, Best Overall: Sawyer Products Mini Water Filtration System at Amazon "It removes nearly 100 percent of bacteria...and protozoa."
Best Personal: Lifestraw Personal Water Filter at Amazon "Perfect for on-the-go drinking while hiking, on a trail run, or in case of emergencies."
Best Lightweight: Katadyn Hiker Pro Microfilter at Amazon "The filter uses an active carbon core to get rid of any bad odor or taste, and to reduce chemicals."
Best Gravity Filter: Platypus GravityWorks Water Filter System at Amazon "The 4-liter filter removes nearly 100 percent of all bacteria and protozoa and is easy to use."
Best Purifying Filter: SteriPEN Ultra UV Water Purifier at Amazon "The pen zaps almost 100 percent of bacteria, protozoa, and viruses."
Best Chemical Treatment: Aquamira Water Treatment Drops at Amazon "The liquid kills waterborne bacteria and viruses...to turn nasty drinking water into potable drinking water."
Our Top Picks
Best Overall: MSR Guardian Purifier Pumps
The holy grail of all backcountry water filters, the military-grade Guardian by MSR not only filters out the nasty stuff from dirty water, but also purifies, creating water free of viruses, bacteria, and protozoa (not just the latter two, which is what most filters do). Use this if you are heading into the wilderness, specifically outside of the continental U.S, or are planning to use this in the most extreme conditions—it can withstand freezing temperatures and drops up to six feet. The pump-styler filter is fast (filters about 2.5 liters per minute) and self-cleans with every pump. The filter will last for more than 10,000 liters of water. The pump weighs 17 ounces and is about the size of a 1-liter water bottle.
Runner-Up, Best Overall: Sawyer Products Mini Water Filtration System
For a long day-hike or a backpacking trip with only one or two people, the Mini Water Filtration System by Sawyer Products is ideal. It removes nearly 100 percent of bacteria (like salmonella, cholera and E.coli) and protozoa (such as giardia and cryptosporidium). The small filter fits in the palm of your hand and easily attaches to the mouth of the included 16-ounce squeeze pouch or fits in a plastic water bottle to use as a filtering straw. If you are looking to fill up a larger water bottle, fill up the squeeze pouch and filter into a different bottle or bladder. A 7-inch straw is also included, in case you wanted to drink right from the nearby stream or lake. Attachments for in-line bladder filtration are sold separately. The lightweight filter weighs 2 ounces and filters up to 378,500 liters.
Best Personal: Lifestraw Personal Water Filter
The 2-ounce Lifestraw Personal Water Filter is as personal as a water filter can get—it’s a solo straw that you dip right into a main water source or into a water bottle. The straw removes nearly 100 percent of bacteria and protozoa and can filter up to 1,000 liters of water. Wear it around your neck with the included lanyard for stops on a hike or stash it in your hip belt for quick access. Although this hollow fiber membrane filter won’t get you liters and liters of filtered water to store, it is perfect for on-the-go drinking while hiking, on a trail run, or in case of emergencies.
Best Lightweight: Katadyn Hiker Pro Microfilter
Another minimal filtering system is the Katadyn Hiker Pro Microfilter, which weighs 11 ounces and is 6 inches high, 3 inches wide, and 2 inches in diameter. It’s ideal for a multi-day backpacking trek with one to three people and won’t take up much space in your pack.
The filter uses an active carbon core to get rid of any bad odor or taste, and to reduce chemicals.
It removes bacteria, protozoa, cysts, algae and other silt at 1-liter per minute, or about 48 pumps. The microfilter comes with a bottle adapter and is also compatible with hydration systems. One filter can clean up to 1,150 liters of water.
Best Gravity Filter: Platypus GravityWorks Water Filter System
If you are backpacking with a larger group of people, a gravity filter will be the most efficient, like the GravityWorks Filter System by Platypus. The 4-liter filter removes nearly 100 percent of all bacteria and protozoa and is easy to use. Simply fill up the dirty reservoir with the unfiltered water, connect it to the clean reservoir, hang them, and hang out. You’ll be sipping on 4-liters of clean water within 2.5 minutes. The filter lifetime is up to 1,500 liters of water.
Best Purifying Filter: SteriPEN Ultra UV Water Purifier
If you aren’t worried about silty water, but are worried about clean water, use the SteriPEN Ultra UV Water Purifier. The pen zaps almost 100 percent of bacteria, protozoa, and viruses. Push the main button once for one liter of water; twice for two liters. From there, stir the pen around in the water for about 48 seconds—a smiley face on the screen will let you know when your water is good to drink. This UV light changes the reproduction process of any bad germs in the water. Recharge the pen from a computer, wall, or solar panel via the USB port. The SteriPEN lamp life is up to 15,000 liters of water; 50 treatments per charge and about 300 overall charging cycles.
Best Chemical Treatment: Aquamira Water Treatment Drops
For a cost effective and extremely lightweight option, choose a chemical treatment, like the Aquamira Water Treatment Drops. The 2-ounces of liquid chlorine dioxide treats up to 30 gallons of water and has a four-year shelf life. The liquid kills waterborne bacteria and viruses (unlike most pump filters) to turn nasty drinking water into potable drinking water. First, mix seven drops per liter of Part A and seven drops of Part B in the provided mixing cap. These will blend after about five minutes and turn yellow. Then, pour the mixture into your water and wait accordingly: 30 minutes for bacteria and viruses, 40 minutes for Giardia, and 45 minutes for Cryptosporidium. This option of water treatment is ideal for backpackers and thorough hikers, or as a back-up in your emergency kit.