Filters in the Field

Aug. 24, 2021

Comparing drinking water filtration methods for backpackers

About the author:

Kelly R. Thompson, CWS-VI, CI, is president of Moti-Vitality LLC. Thompson can be reached at [email protected].


I love to be outdoors, and at times I struggle to disconnect, so last year, in an effort to find a way to do both, I took a beginner backpacking class from a local outdoors group. I could spend an entire article telling you all the things I learned about throwing 35 lb on my back and hiking through the wilderness, sleeping on the ground and not showering for days. As counterintuitive as that sounds, I fell in love with it and am working on a goal of backpacking 250 miles this year.

Hydration is important when backcountry hiking, but so is the weight of the pack on your back. That 35 lb I mentioned would make some of my hiking friends cringe. A gallon of water weighs 8.35 lb, so if you are looking to reduce pack weight, getting rid of water is one of the best ways to do it. The trick is finding the balance between staying hydrated and not carrying too much weight.

I did a 21-mile weekend hike this summer at Jordan River in Michigan. On the first day, the temperature rose to 101°F with a high humidity level. I drank nearly 6 liters of water during the first day and another 5 liters the next day. Had I carried all 11 liters with me, it would have added nearly 25 lb to my pack. Instead, I carried 1 liter with me and brought a 1-lb water filter so I could replenish my water supply as needed using running streams and rivers. Fortunately, there were many easily accessible water sources on this trail. Sometimes water sources may be limited on a trail, so a hiker is forced to carry more water. This amount can be reduced with a water filter.

When I got to the part about filters in the class I took, obviously my ears perked up. It was interesting hearing the instructors talk about filters outside of the water treatment industry. They talked about things like durability, filtering speed, size, field maintenance and weight. It was assumed that a filter would reduce the risk of bacteria, protozoa and viruses. There was little focus on microns or filter media type, except when it came to field maintenance or weight. 

I decided it would be fun and interesting to combine the two worlds—backpacking and water treatment. I reached out to several of the largest and most popular backpacking filter manufacturers that people from the hiking club were using and asked them to send me samples so I could test and review them from the perspective of an industry expert and hiker. I enlisted the help of my fellow backpackers and asked them to give me their real-world opinions of the filters being used in the field.

Backpacking filters and “purifiers” fall into a few different categories, each with their own pros and cons. I have a favorite, but I am more willing to sacrifice weight and ease of use for quality of water. I normally only drink reverse osmosis water. I do not like tannins in my water, and I like it to taste good, even if I believe it is safe to drink. It is true, I hold onto a little of my water snobbery, even while deep in the wilderness. There are some people who are equally fanatical about weight and size. Many long-distance hikers will not carry a filter at all because of the weight. Instead they will use chemical or, in some cases, portable ultraviolet (UV) systems. It should be noted that backpackers and manufacturers view the word “purify” differently than many of us in the industry do. In the backpacking world, a system generally is considered a purifier if it treats viruses as well as bacteria and protozoa. 

Types of Backpacking Filters

Pump filters. These are probably the most common, and they come in a variety of quality levels and size. These units clean water by pumping it through a filter of varying types of media that have a pore size that is too small for bacteria and protozoa—or in some cases, viruses—to move through. I tested several of these this year, including the MSR Guardian Purifier, the MSR Hyperflo Microfilter and General Ecology’s First Need Purifier. The MSR Guardian Purifier pumps water fast, packs up well and is easy to maintain in the field.

Gravity filters. A lot of hikers in my outdoor group swear by these filters. To use, one fills up a bag and allows gravity to push the water through the filter. The nice thing about them is that users do not have to stand by a stream and pump water. Instead, they fill a bag and hang it in a tree to filter while the hiker sets up camp or takes a break. They weigh less than other filters and take up less space in a pack. I tested the Platypus Gravity Works 2.0L filter. Also, the General Ecology First Need Purifier can be used with its carrying case as a gravity filter.

Filter straws. These models treat water as the hiker drinks directly through a straw that doubles as a hollow fiber filter. They are inexpensive, small and light weight. I tested two LifeStraw products. The LifeStraw Universal comes in a bottle adapter kit. Users simply fill a water bottle and put the filter in it. The LifeStraw Flex comes with its own collapsible bottle that filters as you drink. It is not a great option for use with high volumes of water, but is nice for drinking water, especially if water sources are readily available. I did not like that the filter takes up a lot of space in the bottle, which means less water.  

Squeeze filters. To operate a squeeze filter, users fill a bag and squeeze the water through a filter into a bottle, much like rolling a toothpaste tube. Though I did not officially test one, I am familiar with Sawyer’s squeeze filter. They are light weight, comparably less expensive than other filters and easy to field service.

Chemical drops and tablets. This water treatment technique is a favorite of ultra-light hikers who do not want the extra weight of a filter. Chemicals are added to the water, which kills all things living in it. They have the advantage of killing viruses in addition to bacteria and protozoa, but they also can taste horrible and do not improve silt or color. I did not test any of these products.

UV light. I have never actually seen one of these treatment devices used on a trail, but I know there are some ultra-light hikers who use them. These devices zap water with UV light, deactivating living organisms. However, they require batteries and/or chargers to work and are not as effective with colored water. I did not test any of these products.

 A more detailed review of each filter can be found at

I was impressed by how accommodating every company I reached out to was, and frankly, I do not think you can go wrong with any of them in terms of quality and service. It really does come down to a person’s budget and preference.

Even if you never plan to use backpacking drinking water filtration devices while hiking, I think it is pretty cool how big our industry is. It is easy to get so stuck in our own little softener and reverse osmosis world that we miss the other parts of our industry. If you are a dealer and you want to set yourself apart from your competition, consider expanding into some of those other worlds. If you are a sales professional, learning about every aspect of our industry only serves to give you an advantage over your competition. 

All that aside, I can honestly say that I have rarely been more at peace than when watching a sunset over a mountain lake miles away from roads or civilization and sipping a bottle of freshly filtered water. I would recommend the experience.

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