5 Best Ultralight Backpacking Water Filters

Choosing The Right Backpacking Water Filter

Backpacking water filters come in all shapes and sizes. These filters may be similar in function, but their differences can also make or break their performance.

Choosing the right one that fits your needs is crucial for a smooth and enjoyable time outdoors, so we took the liberty of reviewing the best water filters out on the market.

How Do Water Filters Work?

Backpacking water filters may have their differences, but they all have one thing in common: they use hollow fiber membrane technology.

It works like this:

Think of hollow fiber membranes as tiny tubes, like straws. Along the tubes’ walls are thousands, even millions of tiny pores. These pores are so tiny that anything bigger than 0.2 or 0.1 microns can’t go through. To give you an idea of just how wide a micron is, an average human hair strand is around 10-200 microns wide.

So yes, these pores are ridiculously small, and they are very effective against harmful microorganisms since most bacteria and protozoa are bigger than 0.2 microns.

The filtration then happens when dirty water passes through the hollow fiber membranes either through gravity, sipping or squeezing.

What Types of Microorganisms Do These Filters Protect You From?

Most filters are effective against the following microorganisms:


According to the CDC, 1.2 million salmonella cases are recorded each year, with around 450 cases ending in death. Salmonella is a type of bacteria that live in animal and human intestines and is eventually excreted in feces. You can get salmonella infection through improper food or water handling.

Common signs and symptoms of salmonella infection include diarrhea, fever, and abdominal cramps within 8-72 hours of contact. When untreated, this could eventually lead to severe dehydration and shock.


Escherichia coli (or E.Coli, as it is commonly known) is also a type of bacteria found in the gut. While most E.Coli strains are harmless, other types can cause severe gastrointestinal upset, pneumonia and even urinary infections.

E.Coli can be transmitted through food that is not thoroughly cooked, unpasteurized milk and, of course, contaminated water, especially those found in lakes, ponds or sources that can come in contact with animal manure.

Signs and symptoms include bloody diarrhea, vomiting, and even acute kidney failure in some cases.


Giardia is a kind of protozoan parasite. It has a tough shell that protects it from chlorine disinfection. Giardia is most often transmitted through contaminated water and is one of the leading causes of gastrointestinal disease in the US. Giardia infection is common during the summer. Hikers, campers, and backpackers are especially at risk.

Signs and symptoms of Giardia infection include loose, greasy stools, flatulence, and abdominal cramps.


Cryptosporidium or crypto is a microscopic parasite. Like Giardia, it also has a tough shell that is impervious to chlorine and is one of the leading causes of waterborne diseases in the States. Infected people can come down with watery diarrhea within 2-10 days of contact.

Why Can’t Filters Get Rid Of Viruses?

If you’ve noticed, all filters in this list can’t get rid of viruses.

This is because viruses are usually smaller than bacteria and parasites. You will need a device with an even smaller pore size, usually at 0.01 microns. Unfortunately, outfitting gravity and straw filters with 0.01 microns is somewhat counterproductive and difficult since water flow would be very slow.

That being said, only pump-assisted devices are made with pores this size. They’re actually no longer considered as filters but are now classified as purifiers.

If you’ve noticed, we left out the pump filters because while they’re very effective, pumps also weigh significantly more (none of these ultralight filters weigh more than 12 ounces, while the lightest pump filter can easily weigh 20 ounces or more). Plus, pumping takes a lot more effort.

The good news is, waterborne viral diseases are not an issue in the States, where water standards are high. If you’re traveling to developing countries, however, you might want to look into pump filters or other modes of water purification.

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