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Are Backpacking Water Filters Safe? Let’s Look at the Science!

I was walking through the woods and decided to use my water filter device. Then I thought, is this really safe? Are backpacking water filters and purifiers safe? Will I get sick if I drink this water? So, I did some research and looked at the science behind water filters to find my answer. 

The short answer is YES. Water filtration devices and purifiers remove the protozoan spores like Giardia and Cryptosporidium, bacteria, and viruses from water that you take from the stream or lake while backpacking. 

However, you are not out of the woods yet. It is important to understand how water-borne organisms transmit illness and how to protect yourself from them when out in the wilderness.  

Drinking water directly from stream. Can lead to water-borne illness.

Let’s start by taking a look at the three common types of organisms that cause illness when out in the wilderness: Protozoa, Bacteria, and Viruses

Understanding Water-Born Organisms

Pesky little water-born organisms, unseen by the naked eye, wreak havoc with our insides and cause illness.

Fecally contaminated water transmits illness 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 handwashing after going to the bathroom then drinking directly from a stream. Symptoms usually don’t present right away; it may take up to a week and 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 an egg. After drinking these protozoa, the stomach acids cause the cysts to ex-cyst or 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. 

Protozoa in water supply, can lead to giardia.

Symptoms may include the following: 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, 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. 


Common bacteria illnesses include Traveler’s Diarrhea. Traveler’s Diarrhea, aka Montezuma’s Revenge, Tourist Trot, Dehli Belly, 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 rarely life-threatening and easily treated promises days if not weeks of distress to our bodies.

A number of other bacteria and amoeba caused illnesses are more common outside of the United States. These include Dysentery, Escherichia Coli (E Coli), Typhoid Fever, Cholera, Campylobacter. Unlike the ones listed above, these can be more life-threatening so, it is best to learn more before traveling abroad. 


These are the least common for everyday backpackers when it comes to water-born 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 fecally contaminated water transmits these diseases. More commonly found in developing nations where human waste into the drinking water goes unchecked.

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

If you are interested in checking out the best water filters you can find them by clicking here.

Water Filters and Purifier Basics

Staying safe is of utmost importance so it is important to know 1. what you are looking to avoid and 2. how you need to avoid it. Water purifiers are similar 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 (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; remember that several steps are required to make your water safe to drink.  

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 filter. These filters improve the taste of the water by removing bitter-tasting tannins from the source.  

Types of Water Filters and Purifiers

There are several water filters out on the market today. These water filters and purifiers fall into some categories. They include:

Pump Water Filters/ Purifiers:

These are used for pumping large quantities of water for drinking, cooking, and showering. Here is an example:

Sawyer Products MINI https://amzn.to/338tqCFWater Filtration System

Gravity Water Filters/ Purifiers:

The gravity filter/purifier is easy to use and provides for large quantities of clean water. Here is an example:

Ultraviolet Light Water Purifiers:

These water purifiers are low maintenance, easy to use, and work quickly. Here is an example:

SteriPen Classic 3 UV Water Purifier and 40 micron Pre-Filter bundle.

Bottle Water Filters and Purifiers:

Easy to use, lightweight, and fast. Here is an example:

GRAYL Geopress 24 oz Water Purifier for Global Travel, Backpacking, Hiking, and Survival (Coyote Amber)

Squeeze Water Filters:

low volume, easy to use, lightweight, and fast-on-the-go. Here is an example:

Sawyer Products Squeeze Water Filtration System

Straw-Style Water Filters:

These filters are lightweight, easy to use, and fast-on-the-go but are used at the source only. Here is an example:

RapidPure Pioneer Personal Water Purifier Straw

Chemical Water Purifiers:

Low maintenance, easy to use, lightweight, and cost-effective. Chemicals are time-consuming, so not great if you are thirsty now.  Here is an example:

Potable Aqua Germicidal Water Purification Tablets – 50 Count Twin Pack

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.  

How Do I Choose the Right Water Filter and Purifying System? 

There are many filters to choose from but which one is right for you. A few things that you need to think about before purchasing a filter.

Beer frolicking in the water. Beware of water-borne illness.

First, where will you be hiking? In the continental US? Backpacking abroad? Water born 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 both 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 water-born illnesses you may come across.

I researched this and found a great list on NationMaster.com. The spreadsheet provides common diseases by country. So, I turned it into a spreadsheet. Just click here to access the pdf spreadsheet.

Second, where will water be located? I.e. streams, lakes, bogs, or small puddles. If the source is a stream you can use pump filters and if you are gathering water from a small puddle you should try a straw-style filter first. 

And finally, weight. 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.

Avoid Common Water Handling Mistakes

Avoiding contaminations is possible. By avoiding these simple mistakes can make a world of difference.

When you eat foods it is a good and healthy idea to wash or disinfect your hands with hand sanitizer. Also, boiling food for at least 5 minutes kills water-borne contaminants.

Animals are everywhere and drink the same water that you are drinking from the stream. Also, they don’t ask where to go to the bathroom. Scat in animals, just like human feces, carries these water born organisms. Just because you can’t see the scat doesn’t mean that it isn’t there.

Deer drinking water in the wilderness.

Fast-moving streams can provide good clean drinking water 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 bit by mosquitoes and other carriers.

In Conclusion

Even day hikes can result in emptying the water that you packed. To keep safe on the trails bringing a water filter or purifier and a few tablets helps avoid getting sick from drinking the water.

While water is not always safe, a well-maintained water filter is. So, make sure that you carry enough clean water on your trip. How much water should you bring? Find your answer here.