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Backpacking and Hiking Water Treatment Guide

Aaron Zagrodnick



On any hiking or backpacking trip, the ability to procure safe drinking water during the hike is one of the most important logistical considerations for both pre-trip planning as well as while we’re on the trail. Finding the water is of course the first step, and having the necessary gear to properly process the water so it’s safe to drink is the second part of the equation.

Here we’ll look at the main types of water filters and backcountry water treatment methods that are best suited for backpacking and hiking, and elaborate on the necessary reading between the lines that needs to be done when choosing the best backpacking water filters or treatment options for backcountry use.

Hiking and Backpacking Water Filters, Treatment Methods and Considerations

An assortment of various types of backcountry water treatment options

What We Need to Treat and Filter

Microorganisms and Biological Concerns

While protozoan concerns such as giardia and cryptosporidium get the most publicity, concerns are best looked at in a categorical fashion. Starting with biological contaminants from smallest to largest, viruses (example: hepatitis, rotovirus, often smaller than .1 micron) are notoriously difficult to filter as they can slip through most common filter’s pore size.

Luckily, viruses are mostly a concern where there are many other people – for example where you might find untreated sewage. However, it’s always important to remember the source of the water you’re filtering. Bacteria (example: e.Coli, Salmonella, average size greater than .3 microns) are a more common concern in the wilderness as they are spread by both humans and wildlife, but luckily they are larger than viruses and more easily captured by most common filters.

Protozoa are a a bit larger and include cryptosporidium and giardia, and a filter that will filter to 1 micron or smaller is recommended for removal. Concerns that are larger still include tapeworm eggs and unsightly, but not necessarily dangerous, critters of various types in your water such as insect larvae. On many occasions I’ve scooped water from crystal clear mountain streams and upon close inspection, have been quite surprised at what that scoop reveals to the eye – from sticks and stones to tadpoles and worms of various types – not to mention what you can’t see. I prefer to get my calories from my food bag while backpacking, and luckily these larger organisms are of course, very easily filtered.

Backpacking Water Source and Filtration for Microorganisms, Biological, and Other Considerations

Other Treatment Considerations

Many other components can make up the water you’re drinking in the backcountry as well. Chemicals, pesticides and herbicides, heavy metals, tannins, silt, taste and odor, as well as natural particulates of various types will need to be considered. Some of these concerns will only affect smell and taste, others could affect your health. Visible suspended matter is removed by most filters, but tannins and taste / smell can pass through – in my experience even drinking tea colored water however, has been fine.

If your water source is downstream of an area that has seen prior or active agricultural or mining use for example, chemicals and other various components introduced by man could be in the water source, especially as you move further downstream in the water supply chain. To reduce these types of contaminants and concerns we can utilize a purifier or filter that contains a carbon stage, or add a carbon element or step to an existing setup to assist in reducing many of these possible impurities.

Physical Filters and Purifiers

Most water treatment products designed for backcountry use that are reasonably lightweight, will not address all of the above concerns in one fell swoop. Thus, we need to evaluate our backpacking and hiking destinations, as well as our own personal comfort level to find the best compromise. For backpacking in the mountainous wilderness areas of the United States for example, the general consensus is that viruses are usually not of a great concern, and many times our water sources are fairly pure from man-made pollution as we’re getting it close to the source.

In these cases bacteria and protozoa are usually the main concerns. Other backcountry trips may find us filtering water on the banks of a river far from the source, that has passed through many towns before we consume it, perhaps on foreign soil, and the full gamut of contaminants are more of a possibility.

Water filters do just what they say; they filter the water to a certain micron level to remove bacteria and protozoa. Water purification by definition, including options like the First Need XLE will take this all a step further by also removing viruses, though not all products that are officially listed as purifiers will remove or reduce chemicals, heavy metals, tannins, debris, etc. – your water may be purified by marketing general standards, but it will not necessarily be “pure”.

Backpacking Pump Water Filters - Katadyn - PUR Hiker PRO

A classic pump filter works well for pulling water out of hard to reach and shallow sources.

Popular water filters for backcountry water treatment should filter to an absolute pore size of .3 microns or smaller for adequate removal of bacteria, protozoa, and all things larger. Note the absolute part of the pore size equation, as filters listed with a “nominal” pore size will only on average filter to that level. Absolute is a guarantee, and is the number we’re actually interested in.

If you prefer viral protection, you will need an option with a much smaller absolute pore size; as a result flow rate will likely suffer and these types of purifiers are rare. Alternatively some filters combine with other technology to treat the virus part using an iodine or ion exchange process. Backpacking water purifiers that remove viruses physically can be found in the MSR Guardian as well as the LifeSaver Wayfarer pump purifiers. Other options combine a normal filter with a cartridge that contains an iodinated resin for added virus protection, while the Grayl purifier uses an ion exchange process to achieve this goal.

Types of Filters

Physical filtration can be achieved utilizing various types of elements and technologies. The most popular lightweight water filter technology today, hollow fiber filters work by passing water through a multitude of small tubes; tubes that are perforated by many, many, pores so small (rated to the micron) that anything larger than this pore size cannot pass through, trapping any living organisms or non-living matter larger than the pore size. Hollow fiber filters are popular for their light weight and versatility – you can pretty much find one in any filter configuration you prefer – be that as a gravity filter, inline filter, or pump.

Hollow fiber filters can usually be backflushed to help restore flow rate, and flow rate will vary depending on pore size, surface area, and use. The most popular hollow fiber filters are in the .1 to .2 micron range making them sufficient for bacteria and protozoa, and this micron level is usually a good balance of protection, sufficient flow rate, and lifespan. Smaller micron, virus-rated filters also exist in this category as seen with the aforementioned Wayfarer purifier, but flow rate will be slower due to the smaller pore size.

Gravity Water Filter for Backpacking - Platypus GravityWorks System

Gravity filters, an example shown here using hollow fiber filter technology, use the force of gravity to move water through the filter.

Hollow fiber filters cannot be allowed to freeze when wet (the MSR Guardian is an exception) or after they've been used, so on trips where it will freeze at night you’ll need to sleep with the filter in your sleeping bag or carry it in your pocket any time temperatures begin to flirt with freezing during the day – this goes for nearly all other filters using different types of elements as well.

In addition to freezing physical filters also need to be treated with some care in regards to drops and impacts, which could damage the element. Some hollow fiber filters like the Platypus GravityWorks (read our full review here in Issue 25), and the Katadyn BeFree have manufacturer supported integrity tests which are very helpful for a little peace of mind – unlike other gear, you can’t really tell if a filter is working properly or not, without this test.

Other types of physical filter media will use a ceramic element like the MSR EX filter, and the Katadyn Pocket Filter, or utilize a glass fiber element like the venerable Katadyn Hiker Pro. Ceramic filters have the ability to be repeatedly field cleaned. Some filters are entirely self-contained and will need to be thrown away when their flow rate diminishes too much to be of practical use, while others setups will have a replaceable cartridge that fits into a housing.

Approaches to Filtering

No matter what filter technology you end up going with, physical filters are most often utilized in an inline, gravity, squeeze, or pump configuration. The traditional pump water filter requires you to pump the water through the filter element via a hose in the water source, and is a proven setup at both getting you water and providing an ample upper body workout.

Pump filters have moving parts and increase the complication and weight, but these are also great for pulling water out of hard to reach places. The other methods will require you to fill some type of reservoir with dirty water first, by either submerging the dirty water container or bag in the water source or, if it’s one of those shallow or small sources you occasionally may need to use a separate vessel to fill the dirty container, like a mug (boil later to sterilize).

Inline Hiking and Backpacking Water Filter Setup - Sawyer 3-way SP122

An inline water filter connected to a hydration setup treats water as you drink.

Gravity setups like the Platypus GravityWorks and the Katadyn Gravity BeFree let gravity do the work for you, by filling a dirty reservoir with water and by elevating, hanging from a tree branch or rock if possible, water passes through the filter element into a clean container. Inline setups such as the MSR Thru-Link splice into the tubing of your hydration reservoir and your own drinking force filters the water with each sip, while with squeeze setups like the Sawyer Squeeze, you can utilize a combination of gravity and squeezing force to move the dirty water through the filter and the filtered water into a clean vessel or drink directly.

Other options integrate the filter into a water bottle (LifeStraw Go Series) or softbottle (BeFree), where much in the same manner as an inline filter with a hydration reservoir, your drinking or a combination of drinking and squeezing is what filters the water as you go. Straw type options like the Lifestraw Peak (view at REI) are also another strategy, treating water by directly inserting one end into a water source and drinking from the other side of the straw. A straw filter is limited in that you cannot process larger volumes of water and each sip takes more work, and straw filters are perhaps best reserved more for emergency usage.

In whatever case, seek out the cleanest water possible to prolong the life of your filter and for the best flow rate. While many filters can be backflushed or cleaned, this is usually a losing battle over time. Although filters are rated by the gallon or liter in regards to their lifespan, and while it’s a great idea to evaluate this when choosing a filter, take this number with a grain of salt. Clean water is important for other treatment methods as well; in very turbid situations it’s a good idea to allow water to settle in a separate container (in for example, a Sea to Summit Bucket), then treat from the top. Luckily, this is more of the exception than the norm for most of us.

UV Treatment

Ultraviolet treatment options like those offered by Steripen, come in various forms using either normal or rechargeable batteries, and utilize, as with many municipalities, UV light from a special lamp that’s inserted into your water container to neutralize many microorganisms by disrupting their DNA. This process usually takes about a minute and you’ll most likely be treating a liter of water or so at a time. Some other UV devices have come to market that feature an integrated lamp, like the (discontinued) Camelback All Clear, and yet others have been designed to float from the surface of your water vessel.

UV Water Treatment for Backpacking - Steripen Adventurer

UV water treatment uses battery powered ultraviolet light that's inserted in a container to treat many microorganisms.

On the plus side, these UV treatment options are quite effective at neutralizing the things that physical filters have the toughest time with – viruses – and the technology is proven. However, many are not comfortable relying on an electronic and potentially fragile instrument for their main or only wilderness water treatment source.

Additionally, UV light on its own is not sufficient for neutralizing all living organisms that could be present in your water – tapeworm eggs for example, or larger organisms and larvae that may or may not do any harm but may not necessarily be what you want to ingest, nor will a UV product remove anything from the water or improve its composition. If the water is dirty, you’ll be drinking dirty water.

Steripen offers a filter with a 40x40 micron mesh screen that can help here, which is intended to reduce organic matter or particulates. Performance may also be insufficient in murky water, requiring pre-filtration. All said, this is an excellent technology as long you’re aware of the limitations; I utilize a Steripen Adventurer Opti as a secondary treatment with a hollow fiber filter on any trip where I desire viral treatment.

Chemical Treatment

Chemical treatment usually utilizing chlorine dioxide (Aquamira) or Iodine (Potable Aqua) and on occasion some other chemicals like household bleach or other chemicals that produce chlorine, like Aquatabs can be effective, but like anything this category has its share of pros and cons. In contrast to physical filters and like UV treatment, chemicals are again effective against viruses, but often take longer (hours) to work on such concerns as cryptospordium (4 hours) and these products will add a taste to your water; other products are not suitable for cryptosporidium whatsoever. Advocates for chemical treatments praise the ease of just adding the treatment right into their water bottles and allowing the treatment to take place as they hike.

To be honest, most of my thought goes into making sure my drinking water source is either free of any chemicals or how to reduce or remove them should there be any chance of them being present, so chemical treatment is a bit counter-productive from my point of view, and options like iodine are not an option for pregnant women or those with any type of a thyroid issue. Iodine and chlorine (i.e. bleach) on their own, are not effective against cryptosporidium.

However, this method is lightweight and over the years has been popular with ultralight backpackers, though decreasing in recent years with the increased availability of very light hollow fiber filters like the Sawyer Mini. In this category, other devices have seen the market over the years that create a solution with salt to create an oxidant solution that you subsequently dissolve in water; but as with other chemical treatments, with a 4 hour wait time these are not the quickest of options.

An example can be found in the discontinued MSR MIOX. These devices seem to come and go from the market. Chemical treatment may also be integrated with some filters to move them into the purifier category. As with boiling, chemical treatment can be a good backup to bring as well or to utilize in conjunction with other methods.

Filtering Downstream and Muddy - Silty Water Sources While Backpacking

Hundreds of miles from the source, I took extra steps in my treatment process at this backcountry location.


Boiling water is an excellent way to neutralize microorganisms that might be present, but it takes a while, requires a lot of fuel, and let’s be honest, on a hot summer day, who wants to drink steaming hot water when we could be drinking that crisp and cold water from a mountain stream? As such, boiling can be tough to utilize as a main water treatment method on most 3 season backpacking trips, but it’s an excellent method to keep in mind as a backup method should your filter or other method fail you.

In winter however, melting snow for water may be your best and only option. Be sure to bring a big pot (my Evernew 1.3 works well solo) and a stove that will work well during continued usage in cold conditions like the MSR WindPro II – read our review in Issue 33. Opinions on how long to boil water vary widely; the CDC suggests bringing water to a rolling boil for 1 minute, or for 3 full minutes at altitudes above 6562 feet (be sure to check that 2 on the end of your altimeter!). Data suggests however that pathogens are neutralized at lower temperatures; in the end in depends on heat and time but luckily, both are achieved by bringing your water to a boil and after removal from heat.

Carbon Filtration

As we’ve seen, the technologies used above are all mainly designed to thwart microorganisms. If improving the taste and smell of your water, or if any agricultural and / or industrial contamination is a concern, look for a system that integrates filtration technology combined with a carbon stage that will improve and / or reduce, but not necessarily eliminate, these concerns.

Backcountry Water Filtration and Using a Carbon Element to Improve Water Quality

If desired, a carbon element can be integrated into an existing system using a modular approach to filter water further.

This will increase the weight of your system, and possibly the cost of replacement elements, etc., but there is of course no free lunch. The Grayl UltraPress and Katadyn Hiker Pro are all examples of filters with integrated carbon filtration – or if you’re like me and have settled on a treatment method that does not address this concern, but you may occasionally head out on a trip where some of these concerns would be nice to cover, you can always splice in an add-on carbon element (I use an add on GravityWorks Carbon Element) for this purpose when needed.

My Approach

For a complicated issue, there are unfortunately no one size fits all solutions and in the end, when we’re concerned about not carrying extra weight, it all comes down to a compromise and what each one of us is most interested in removing from our water. Luckily there are many lightweight and effective options out there to choose from. For general backpacking we should expect to find an option that will treat what we’re concerned with for around a pound or less. About half a pound is usually doable, and lighter options of just a few ounces are very realistic to target. The best backpacking water filter or water treatment method very much depends on the task at hand.

Platypus GravityWorks Water Filter Element

Most of my trips are very well served by standard hollow fiber filtration technology; as with all of us most likely, my preference is to backpack into areas where the water is already fairly good. As such I’m not usually concerned about viruses or pollution, (both a Steripen and carbon filter have a spot in the gear room for such destinations to use in conjunction with a hollow fiber filter), and I like to target the removal of bacteria, protozoa, and the removal of larger critters no matter their parasitical intent or lack thereof.

The hollow fiber filter also has that added benefit of giving your water a good scrub; removing particulate matter. I really like a filter that has a manufacturer supported integrity test as well, so it essentially comes down to the cartridge for me. The Platypus GravityWorks cartridge fits all of the above criteria, and it just so happens the whole setup it comes with works well and is pretty darn convenient to use both on the trail as well as in camp.

For a complete list of backcountry-ready, tried and tested backpacking water filters and treatment methods that you can sort and filter by all the main points we’ve discussed in this post, check out this page at REI.



Recommended Comments

Nice summary.

The thing about mechanical devices is that they eventually fail. And by fail I mean break. It's inevitable. Not a big deal for a weekend hike, but for longer trips I no longer rely on filtration devices (other than a bandanna).

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Aaron Zagrodnick


Thanks! I think water treatment unfortunately is one backpacking gear consideration where it’s hard to ever be 100% satisfied with your choice, and agree that’s its good to keep things as simple as possible. Like any good vehicle, a mechanical filtration device will eventually reach the end of its service life, I guess all we can hope is that with good care we get decent mileage out of them before that happens. :)

I use a filter as my main filtration solution and value reliability as well - I think if you go that route inline or gravity setups will offer more reliability with fewer moving parts, at that point it’s mostly the cartridge itself to be concerned about. (And even if it begins to clog, at least we can still get clean water here, albeit slowly) Frequent maintenance (backflushing), and using the cleanest source water possible both will help prolong service life, but of course eventually we all hopefully hike enough that it must be replaced and I’ve replaced my share of cartridges for sure. I’ve used filters on up to 10 day stretches - that was with a more traditional pump - and the current generation of hollow fiber filters have worked well on longer trips for me as well, however I do try to seek out cleaner water and backflush the filter. For those back to back long stretches, thru-hikes, or even with season after season hiking weighing the reliability, as well as the cost and convenience of replacing what you’ll need for any method is definitely good to think about, be it cartridges, chemicals, batteries, etc. 

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