Are Backpacking Water Filters Safe? (Let’s Look At The Science!)

Water filters are a key part of many backpackers’ equipment. When out on long treks, it’s not always possible to carry enough water on your back, but this can be a problem even for short day hikes in hot weather. This leaves many wondering if backpacking water filters are actually safe.

Backpacking water filters are safe. They remove the protozoan spores like Giardia and Cryptosporidium from the water, along with bacteria and viruses. This allows you to safely drink water from streams and lakes when backpacking, and there are lots of different options to choose from.

It is important to understand how waterborne organisms transmit illness and how to protect yourself from them when out in the wilderness. Below, we’ll go into more detail about these microorganisms, and consider the best water filters on offer for backpackers.

Understanding Waterborne Organisms

Pesky little waterborne organisms, unseen by the naked eye, wreak havoc with our insides and cause illness. Water that contains fecal matter can transmit illnesses to our bodies. For example, when a deer, bear, or other animal has a bowel movement in or near a stream, contamination may occur.

Other times it can be due to improper hand washing after going to the bathroom then drinking directly from a stream. Symptoms usually don’t present themselves right away. It may take up to a week for them to show, and they may last for another week, if not longer.

Our body, when under attack, will do its best to get rid of the contaminants. It does this by turning on the gastrointestinal faucet and causing an exit of bacterium, amoeba, and protozoa out of the body by way of diarrhea. 


Protozoans like Giardia and Cryptosporidium exist in water supplies as a cyst-like egg. After drinking these protozoa, the stomach acids cause the cysts to hatch. When they arrive in the intestines the protozoan begins to reproduce and cause the diseases that we see such as Giardia and Cryptosporidium. In this state, they can wreak havoc on your body. 

Symptoms may include persistent diarrhea, weight loss, abdominal cramps, nausea, dehydration, and general weakness. It is important to note that these symptoms don’t usually start right away, and it may take up to a week to exhibit symptoms, and they can last for a couple of weeks after that. The best way to keep the protozoan out of your system is through a water filtration device


A common bacterial illness is Traveler’s Diarrhea. Traveler’s Diarrhea, also called Montezuma’s Revenge, Tourist Trot, Delhi Belly, or Aztec Two-Step, comes from a common bacteria found in many parts of the world: bacterial enteropathogens.

Common bacteria found within the United States include Escherichia Coli (E. Coli), Salmonella, Campylobacter, and Shigella. Symptoms can range from mild to severe and include nausea, diarrhea, vomiting, abdominal cramping, bloating, malaise, fever, and urgency. While not always life-threatening and often easily treated, these illnesses promise days – if not weeks – of distress to our bodies.


These are the least common for everyday backpackers when it comes to waterborne illness. However, we must always be on our guard. The most common viruses associated with backpacking include Hepatitis A and E. These viruses cause liver damage through contact with the Hepatitis A and E viruses.

It is widely known that drinking water contaminated with fecal matter transmits these diseases. They’re commonly found in developing nations where human waste into the drinking water goes unchecked.

Hepatitis A and E symptoms can include jaundice of the skin and eyes, loss of appetite, dark urine, pale stools, an enlarged, tender liver, abdominal pain, nausea, vomiting, and fever. These diseases are serious and cause liver damage and eventually death if left untreated. 

Water Filters And Purifier Basics

Water purifiers are similar to water filters in their mechanisms in that they both strain the water to remove the contaminants. Water filters strain protozoan cysts (50 microns) and bacteria (0.2 to 2.0 microns) effectively, and water purifiers use chemicals to kill viruses that are too small for most filters to catch.

The chemical most often used is iodine because it is more effective in activating protozoa (like Giardia). Iodine takes about 30 minutes to work and treatment time changes with the outside temperature. So, be sure to read the directions on the iodine bottle.

The Role Of Pre-Water Filters

Pre-filters remove small debris, like leaves, when taking water from a forested area. Pre-filters remove the larger items before they get to the main filter. These filters improve the taste of the water by removing bitter-tasting tannins from the source too.  

Types Of Water Filters And Purifiers

Pump Water Filters/Purifiers

These are used for pumping large quantities of water for drinking, cooking, and showering. An example of this is the Sawyer Products MINI water filtration system. It’s lightweight, claims to remove 99.9999% of bacteria, and comes with a straw and drink pouch. It’s rated for up to 100,000 gallons of water.

Gravity Water Filters/Purifiers

The gravity filter/purifier is easy to use and ideal for providing large quantities of clean water. An example is the GravityWorks from Platypus. It has a 2 liter capacity, and is designed to be lightweight and easy to use.

Ultraviolet Light Water Purifiers

These water purifiers are low maintenance, easy to use, and work quickly. An example is the SteriPen, which uses UV light to purify the water, eliminating 99.9% of bacteria, viruses and protozoa. It’s fairly small, and it can purify your water in less than a minute.

Bottle Water Filters And Purifiers

Bottle water filters are very easy to use and fast acting. A good example of this is the GRAYL Geopress water filter. It’s a little on the heavy side, but as it functions as your bottle too, you can treat it like a normal water bottle. This has advantages over the pouches and straws of other designs in that it’s just easier to use and not prone to bursting.

Squeeze Water Filter

Squeeze water filters are low volume, easy to use, and lightweight. An example of these is another Sawyer product, this time it’s their Squeeze Water Filtration System, and these squeeze water filters come with flip top sports caps for easy use and consumption, and they hold up to 32 ounces of water.

Straw-Style Water Filters

These filters are lightweight, easy to use, and fast acting, but need to be used at the water source. An example is the RapidPure Pioneer Personal water purifier straw, and it’s great for consuming water at the source without having to carry it on the trail with you. It’s super lightweight, coming in at less than 3 ounces.

Chemical Water Purifiers

These are low maintenance, easy to use, lightweight, and cost-effective. Chemicals take time to work, so not great if you need drinkable water instantly. A good option are Potable Aqua purification tablets, and they provide you with drinkable water within just 35 minutes. Bear in mind that chemical purifiers tend to be the most expensive option.

Boiling Water

Boiling water is highly effective and inexpensive. It requires little maintenance and provides a large volume for all-around use. On the flipside, boiling water takes more time and is best when performed at the beginning or end of the day. Plus, without a filter, you will only be killing bacteria and protozoa etc, and won’t be able to filter out things like microplastics.

How To Choose The Right Water Filter And Purifying System

First, consider where you will be hiking. Waterborne organisms vary depending on where you travel. For example, the United States is known for bacterial and protozoan diarrheas with pockets of Hepatitis A, while Africa has diarrheas, Hepatitis A and E, as well as Typhoid. 

So, how do you know which system to use? Whether traveling around the world or within the United States, it is important to know what types of waterborne illnesses you may come across. Do your research, and check with government websites of the areas you’re visiting for up to date information.

Second, consider what sources of water you’ll be using, such as streams, lakes, bogs, and even small puddles. If the source is a stream, you can use pump filters, and if you are gathering water from a smaller puddle, you should try a straw-style filter first. 

And finally, consider the weight of the filter. If you are a minimalist and want a product that is as light as possible, try using chemicals like iodine, straw style, or squeeze filters. If weight isn’t as much of an issue, then any of the options above will suit.

Avoid Common Water Handling Mistakes

When you eat food, it is a good and healthy idea to wash or disinfect your hands with hand sanitizer afterwards.

Animals drink the same water that you are drinking from the stream, and may use it as a bathroom too. So, just because the water looks safe, you should still always use a water filter. Fast-moving streams can provide good clean drinking water as is, but it is not worth the risk when out backpacking.

Areas with heavy rainfall or boggy areas can carry more than just waterborne illness. They can also host a wide variety of insects that carry disease. It is best to wear repellent when out in the wilderness, so you don’t get bitten by mosquitoes and other disease carriers.

Final Thoughts

Water filters are safe for backpacking, and they come in many different forms. You’ll find lots of options online and in stores, but it’s important to choose one that matches your style of hiking. Consider where you’ll be hiking, where you’ll get the water, and the filter’s weight before you buy.