The 6 Best Backpacking Water Filters to Keep Your Adventures Illness-Free

Water is heavy and a pain to carry hiking. When made safe to drink, outdoor water sources are the answer. Here are the best backpacking water filters and purifiers to keep you from coming home with a stomach bug.

Your Four Options for Treating Water on the Trail

Even the most pure-looking mountain streams can have bacteria and protozoa in them that will make you sick, such as parasitic giardia and cryptosporidium. If you’re traveling internationally, water may have viruses in it too. So, if you’re not sure about water quality, it’s time to listen to your grandma when she told you, “an ounce of prevention is worth a pound of cure.”

Let’s start with a rundown of all the ways you can make water safe to drink because it’s a wide range.

• Boiling Water: Long before the days of modern filters, we always boiled water before drinking it on camping and backpacking trips, and it works very well. You can even use a piece of old pantyhose or a coffee filter to screen out grit and leaf debris before you put the water in your pot. The CDC recommends boiling water at a roil for at least a minute to kill germs and parasites, and longer at high elevations. The problem with boiling is it’s hard to do in large quantities, it uses up stove fuel, and in the summer, you have to wait if you want cool water to drink.
• Backpacking Water Filters: Water filter systems—not to be confused with water purification systems (which we’ll talk about in the next bullet—give you cool water to drink right away. But while they take out bacteria and protozoa, they don’t remove viruses. There are lots of options in this category, including small systems for ultralight backpacking, gravity systems that will handle more volume, and pump systems.
• UV Water Purifiers: If you’re traveling internationally to areas that potentially have viruses in the water, then you’re going to need a water purification system. Options here include ultraviolet purifiers that kill bacteria, protozoa, and viruses. While they work quickly, they’re not suitable for large quantities of water all at once and require batteries.
• Chemical Treatment for Water Purification: Many chemical systems on the market are highly effective in treating water. Like UV systems, they kill everything, including bacteria, protozoa, and viruses. Most use chlorine dioxide, which leaves behind virtually no aftertaste or color. The downside here is the wait time. While most pathogens are killed in about 30 minutes, cryptosporidium takes four hours. On the upside, you can treat large amounts of water at one time.

How To Pick The Right Water Treatment Option For You

When deciding what kind of backpacking water filter or other water treatment option to buy. There are generally four primary considerations:

• Where you’re going: If you’re traveling internationally, then you need a purification system, which kills all bacteria and viruses. In the U.S. and Canada, a filter system is all you’re likely to need since there are no viruses in the water.
• Weight: If you’re backpacking long distances, then literally every ounce is a major consideration, and you’ll want something small and light.
• Volume: When traveling with a group, or if you plan to stay in the same place for days, then big-volume water treatment systems make the most sense.
• Price: While there are inexpensive options, there are plenty of big-dollar pump systems too. Don’t spend a lot if this is not a piece of gear you plan to use often.

Best Overall Backpacking Water Filter: Platypus GravityWorks

I’ve been using the two-liter version of the Platypus GravityWorks system for several years, and I’m very happy with it. I think it’s a good compromise between price, weight, and capacity. Platypus makes a four-liter version too for larger groups. You get a “Dirty Reservoir” bag to collect water from a lake or stream, and then you hang it up higher than the “Clean Reservoir” with the hose and in-line filter between. You just walk away and come back about 10 minutes later when all the water in the dirty bag has been processed. The whole kit rolls up into a fairly small package and is easily stuffed in a backpack. The only challenge has been thoroughly drying the reservoirs when I get home for storage. I’ve solved this with a cheap fish tank aerator and hoses to blow air inside the bags for a few hours until they’re completely moisture-free. You can also store the bags in your freezer, which I do with my Camelbak bladders when not in use.

Best lightweight and cheap filter: Sawyer Squeeze

If you’re planning a long-distance backpacking trip or you just want the cheapest option, then the Sawyer Squeeze is for you. At just three ounces, the nearest thing I can compare this to is a juice box for kids. You fill the bag with water and then screw on the filter and drink through it. It’s inexpensive and fast for small amounts of water, but not good if you want to process large volumes.

Best Pump Filter: Katadyn Hiker Pro Transparent Water Microfilter

Pump water filter systems are the heaviest option, and you have to sit there and pump all the water you want to use through them. They do have one key advantage, however. Because you can position the intake hose wherever you want to, they’re the best for water running through narrow cracks or shallow water sources where it’s hard to scoop water into a reservoir without also getting a lot of crud too. I like the Katadyn Hiker Pro for its price and reputation for reliability.

Best UV Purifier: SteriPen Ultra

If you’re traveling outside the U.S., Canada, or the U.K., then a system that also kills viruses is a good idea. UV purification systems work by killing bacteria, protozoa, and viruses with ultraviolet light. Like filtration systems, they give you cool water to drink straight away but aren’t great for processing large amounts of water quickly. You’ll also need to do some sort of pre-filter if the water is murky or full of debris. The SteriPen Ultra is super-convenient to use. You simply stick it in the small-mouth opening of a plastic water bottle, flip it upside down, shake the water for about 90 seconds, and you’re done.

Best Chemical Treatment: Potable Aqua Chlorine Dioxide Water Purification Tablets

If you’re willing to put up with the wait time, chemical water purification is an excellent way to treat large amounts of water. Potable Aqua Chlorine Dioxide Water Purification Tablets kill bacteria, protozoa, and viruses. The tablets are very lightweight and easy to use. Iodine-based systems work faster, but chlorine dioxide doesn’t have the aftertaste. Remember that while it only takes about 30 minutes for most pathogens, chlorine dioxide takes four hours to wipe out cryptosporidium.

Best for Travel: GRAYL GEOPRESS

While not great for backpacking because of its weight and size, the GRAYL GEOPRESS deserves an honorable mention here because it’s perfect for those south-of-the-border trips where the water can be sketchy. It’s a purifier, so it takes care of everything, including viruses. I like it for filtering hotel water from the tap, and it means I’m not lugging around a ton of bottled water with me.

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If you’ve never gotten a stomach bug from drinking contaminated water, trust me, you don’t want to. Some of the nastier kinds can even linger up to a year or more—not to mention what a virus might do to you. A backpacking water filter or some other kind of water purification system is not a large investment, and it’ll keep you from being haunted by the Ghost of Camping Trip Past.