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  • Writer's pictureWinston Endall

How to Get Safe Drinking Water in the Backcountry

Updated: Oct 6, 2019

Katatdyn BeFree Water Filter. Before and after. Imagine what you can't see. Photo Credit: Catharine Gerhard

When you get right down to it, we need food, shelter, and water to survive. We have other articles that cover food and shelter so this one is going to delve into how we can get safe drinking water in the backcountry.

The average person on the trail needs at least 4 liters of water per day, which weighs 4 kilograms (8.8 lbs). As such, if you tried to carry all the water you need for a trip you would quickly have so much weight in your pack that it would be too unwieldy to carry.

This is where finding and processing natural water sources come in. Streams, lakes, springs, and swamps can all be wild water sources and each has various challenges. Since we have no easy way to test water for pathogens it is best to treat all sources like they are contaminated.

Waterborne illnesses from bacteria, parasites, and viruses.

Natural water sources such as rivers and lakes often contain micro-organisms that that can make you sick. Water gets contaminated in many ways including animals and people pooping in or near the water source. So make sure when you are going to the bathroom, you are at least 200 feet from a water source and bury your waste in a hole at least 8 inches deep.

Waterborne illnesses can be caused by bacteria, parasites, and viruses. Depending on where you are the risks vary so it is a smart thing to research where you are going in the backcountry. A high mountain stream is less likely to have viruses than a river near human habitation, but things like Giardia and Cryptosporidium can be found in most water sources.

Depending on the condition you contract it can result in severe diarrhea, vomiting, stomach pain, and fever. As well, Hepatitis is a risk in third world and tropical countries where human waste enters the water supply.

Dehydration is a serious risk when you contact any of these illnesses.

Without getting into the microbiology too deeply, if we treat all water sources found in the wild as contaminated and process it accordingly, we will reduce the risk of contracting an illness. Waterborne pathogens can either be removed with filtration or killed via various methods such as chemical treatment, boiling or Ultra Violet light.

Another area of concern is water contamination with industrial chemicals and heavy metals in areas of mining and other extractive industries. In areas that have a history of mining or fracking, groundwater may test with high levels of mercury, lead, or other heavy metals. Do your research before heading into an area so you know what to prepare for.

How to choose a water source

When looking for a water source in the wild, the ideal is clear moving water like a creek or a stream. You are looking for water that is free of particulate matter such as silt or organic materials like algae. If the option exists, avoid using standing water, as it will be more likely to have a higher concentration of bacteria or parasites but sometimes you can't avoid it.

Depending on what water treatment system you are using it may be as simple as scooping up a bottle to add chemical treatment or find a small waterfall to make it easier to fill your water bag for gravity or squeeze filter.

What to do with cloudy or dirty water

When faced with a high level of turbidity (cloudiness) you should either pre-filter or let the particles settle before processing the water. If you try to micro-filter cloudy water directly you will very quickly clog your filter rendering it inoperative.

An easy way to remove most of the particulate matter from the water is pre-filtering with a cloth such as a bandana or a sock. Using your cooking pot or a spare bottle, scoop up water and then pour it into a bottle with a cloth over the opening to filter out most of the particles.

If you have a dry bag or spare bottle you can fill it with water and wait for the particles to settle to the bottom before processing the water on top with micro-filtration or chemical treatment. Once the particles have settled, carefully pour the clear water into another container for treatment.


Microfilters come in a number of different configurations but all of them are fine enough to filter out bacteria and parasites. A few models will even filter out viruses. Generally, the pores of a micro-filter are .1-.3 microns in diameter which is small enough for bacteria and parasites while models such as the MSR Guardian and Grayl OnePress Global will remove all types of pathogens.

For most water sources in Canada and the US, backcountry filtration will remove all of the pathogens that can make you sick. The exception is waterways that may contain human waste or farm runoff.

Pump filters

These filters will have a hose to go into the raw water and you pump with clean water coming out the other end. Pump filters use either a micro hollow fiber or ceramic membrane that has pores small enough to trap pathogens.

They have the advantage of being simple to operate and many are field serviceable so if the flow has slowed down due to particulate build up they can be cleaned.

Ceramic filters like the Katadyn Pocket Filter have the advantage of long life span but come with a high price tag. The ceramic is more brittle so could crack if dropped so care should be taken.

Katadyn Pocket Filter

The MSR Guardian is the premium pump filter as it will filter bacteria, parasites, and viruses. It has a flow rate of 2 liters per minute and is self-cleaning. The filter has a lifespan of 10,000 liters making it one of the longest-lasting on the market. This comes with a high price tag and large size and weight (1 lb). But it might be the best option if you are going into an area where viruses are an issue.

MSR Guardian Water Purifier

Compared to other types on the list, pump filters are heavier, bulkier, and more expensive. The other downside is you have to pump which can be tiring and time-consuming.

Pump filter pros and cons


  • A reliable way to filter water. MSR Guardian will even do viruses.

  • Most are field cleanable

  • Most have replacement filter cartridges available


  • Relatively heavy and bulky

  • Can be expensive

  • You have to pump

Gravity filters

Gravity filters have a bag you fill with dirty water and hang with gravity moving the water through the filter. They are available with water bags up to 10 liters making them great for groups as it is a quick way to process a lot of water with no effort. Once you hang it up you have clean running water on demand.

The Platypus gravity filter has both dirty and clean bags making for the easiest system to operate without any monitoring. Just fill the dirty bag and hang, with the clean water filtering into the clean bag. The clean water bag can be used for water storage as well. They are available in 2 and 4-liter sizes.

Platypus Gravity Filter

The MSR Gravity Works doesn't have a clean bag but the fitting on the end of the hose will thread onto water bottles. It will fit Nalgene bottles or MSR Dromedary water bladders. It has a pre-filter in the dirty water bag making it easier to keep the filter clean. It is also available in 2 and 4 liter-sized bags.

Any gravity filters with the filter mounted in-line on the hose can be backflushed to increase the lifespan of the filter.

Katadyn BaseCamp

This like the MSR doesn't have a clean bag. You have the dirty water bag with a hose running out from the filter. The hose has a shut off valve. Since it is a standard size hose you can add fittings to make your own clean water bag. It comes with a 10-liter bag making it good for large groups. From experience, make sure you pre-filter the water as the flow rate can decrease substantially with particulate matter in the water.

Katadyn BaseCamp

Gravity Filter Pros and Cons


  • No pumping. Just hang and go about your other tasks.

  • Good flow rate when new.

  • Back flushable to maintain flowrate


  • Can clog easily due to the narrow mouth of the filter

  • Heavier and bulkier than other filters on the list

  • The bag can be hard to fill from shallow water sources.

Squeeze Filters

Squeeze filters generally work by filling a soft bag or bottle, threading on the filter and then squeezing the bag to force the water through the filter.

While you can drink straight from the filter, the standard practice is to filter into bottles or a hydration bladder. Always wipe water from the outside of the bag before turning it over to squeeze into a bottle as dirty water running down the bag can lead to cross-contamination.

Most squeeze filters are good at filtering bacteria and parasites from the water. Sawyer's line of filters along with the Katadyn BeFree stand out for ease of use, reliability, and lightweight.

Sawyer Filters

Sawyer has three filters: the Mini, Micro, and Squeeze. I would avoid the mini as it has an annoyingly slow flowrate. The other two have a flow rate of around a liter per minute.

When you buy a Sawyer filter they come with dirty water bags but you also have the option of using disposable bottles like Smart Water or pop bottles as the filter has the same thread.

If you use Smart Water bottles as your water carrying container you then have a backup for the squeeze bag without carrying anything extra.

With Sawyer filters always carry a spare sealing washer as it won't work if it falls out which has happened to me. Sawyers also comes with a syringe you can use to backflush the filter to help maintain flowrate.

The Katadyn BeFree

The Katadyn uses a more open filter design which makes for a higher flowrate. When new you can expect around 2 liters per minute. They come in three bag sizes .6, 1 or 3 liters. The bags are very pliable making it easy to squeeze.

Because the filter is wider it won't fit on standard water or pop bottles but they are compatible with Hydroflask water bags. This will allow you to bring a backup bag.

They are cleaned by swishing the dirty end of the filter in clean water, making it easy to keep clean in the field.

Katadyn BeFree

Squeeze Filter Pros and Cons


  • Lightweight and small

  • Inexpensive

  • Most have a relatively high flow rate. (1 liter per minute or higher)

  • Flushable to restore flowrate


  • Limited Lifespan compared to some pump filters (usually around 500-1000 liters in real life)

  • Risk of cross-contamination if dirty water runs down the bag

  • Bags can be fragile

Straw Filters

These may be the simplest to operate as you put one end in the water and suck on it like a straw. Since they only operate on suction the flow rate is very low. Lifestraw popularized this type of filter but Sawyer filters can be used this way as well using the included rubber tubing.


Having tried a few straw filters I don't recommend them as your main means of water purification as there is no way to process larger amounts to take with you.

Grayl One Press Global

Closely resembling a coffee press the Grayl One Press Global is unique in a number of ways. It works by removing the filter, filling the bottle with water to be cleaned and then pressing the filter through the water like you are making coffee with a press.

Grayl One Press Global

It is one of the only filters that not only remove bacteria, parasites, and viruses but also removes chemicals such as chlorine and heavy metals such as lead.

The downside is only 710 ml per bottle and a filter with only a 250-liter lifespan. It also weighs 1 pound putting it on par with the MSR Guardian which has a filter life of 10,000 liters.

Care and Maintenance of Water Filters

When you get home from a trip you should disinfect your filter as per the manufacturer's directions. This usually means running water through it treated with bleach to kill anything that the filter trapped. After this, you want to let it completely dry before you put it away. Otherwise the next time it may be overrun with bacteria build-up.

And in cold weather, you want to make sure your filter doesn't freeze with water in it. The water freezing can crack the filter on the inside rendering it ineffective. If you expect it will get below freezing overnight put the filter in a freezer ziplock bag and put it in your sleeping bag.

Chemical Treatment

Chemical treatment is usually chlorine dioxide in the form of drop and tablets. This is similar to what your local water supply will do to process safe drinking water. You add the specified amount to your water and wait for it to kill the bacteria and viruses. It can render the water safe to drink but chemical treatment can add a chlorine taste and doesn't remove particulate matter such as sediment.

Iodine treatment is also available but it is neither as effective or as safe to use. Iodine will only kill bacteria and viruses. Prolonged use of iodine can have a negative effect on thyroid health and cause diarrhea, nausea, and upset stomach as well as adding a metallic taste to water.

Aquamira and Pristine brands offer a two-part liquid system that will kill bacteria, parasites, and viruses but with a caveat. To treat 1 liter of water you mix 5 drops of each liquid in the supplied micro-cup and wait 5 minutes for it to activate. At that point add it to your water. You need to then give it 30 minutes to kill bacteria, giardia, and viruses but it takes around 4 hours for it to kill cryptosporidium. Since we have no way of knowing if the water contains this parasite then you are taking a risk if you don't give it the full time.

You can also get chlorine dioxide in tablet form which doesn't require mixing. Aquamira and Katadyn versions are readily available online and at most outdoor stores. Each tablet will disinfect 1 liter of water. They have the same issue with needing about 4 hours to kill cryptosporidium.

If you have a relatively large water bag like a 4 liter MSR Dromedary, you can bulk treat water overnight which will give you the time for the chlorine dioxide to kill the cryptosporidium.

There are other chlorine tablets from Aquatabs and Pristine that will kill bacteria, giardia, and viruses but even with enough time aren't rated to kill cryptosporidium.


Another reliable way to disinfect water is by boiling. If you bring water to a boil for 1 minute (3 minutes above 5000 feet of altitude) you will kill any pathogens.

The downside is that it is time-consuming, uses extra fuel, and you have to wait for the water to cool before drinking.

If you have a metal container like a pot or single-walled stainless steel bottle you can also use a fire for boiling water rather than your stove to save fuel. I consider boiling as a back-up method most of the time but if I am going to boil water for food or a hot drink I will often just scoop it out of the stream and bring it to a boil for a minute rather than filtering.

UV Treatment

This is using ultraviolet light to kill pathogens in the water. Steripen is the most popular brand of UV water treatment. They have a battery-powered bulb that gives off ultraviolet light that is rated to kill bacteria, viruses, and parasites.

To treat the water you just fill a bottle or pot and stir the UV light in the water for 90 seconds. This doesn't remove the pathogens but makes them inactive and unable to reproduce.

When using UV light for water treatment you need to make sure the water is free of particulate matter so pre-filtering is often a necessity. Steripen makes a pre-filter that fits on most wide mouth bottles but you can also use coffee filters or a bandana.

The downsides are being fragile, relying on batteries, and are reliant on long enough exposure.

What to do in winter

In winter with frozen waterways and snow cover, your main way of getting drinking water will be melting snow. As such, boiling will be your logical disinfection method. As per the guidelines above, once the snow is melted bring it to a boil for 1 minute at sea level and 3 minutes above 5,000 feet.

When melting snow always put a little liquid water in the bottom of your pot before adding snow otherwise you will scorch the bottom of your pot and your water will end up tasting like burnt popcorn. Since snow is more air than water until some melts it will be like you are heating an empty pot.

It is also important to bring insulated bottle holders or insulated hydration bladder to keep your water from freezing during the day. At night you can keep a bottle of water in the foot of your sleeping bag to keep it from freezing overnight.

U.S. Center for Disease Control Recommendations

When you look at the recommendations from the Center for Disease Control in the United States, the consensus is boiling or a combination of filtration and then chemical (chlorine dioxide) or UV treatment if you are unsure of the quality of water. In high alpine, environments with little risk of human or farming contamination, micro-filtration or chlorine dioxide with appropriate wait times are usually considered safe.

For more information check out this link.

Recommendation for Group Camping

4 liter MSR Gravity filter with an additional clean water storage bag with chemical backup if the water is in question.

This kit is simple to operate, reliable and doesn't require any work once set up. It will filter 4 liters at a time and that water will only take about 6 minutes when the filter is new. It is easy to backflush in the field and the filters are light enough that it is easy to carry a spare for the group. If there is a concern of viruses in the water then the filtered water can be treated with chlorine dioxide for a reliable and relatively quick treatment.

Recommending for solo trips or thru-hiking

Sawyer Squeeze or Katadyn Befree with chemical backup

As the recommendation for group use, the squeeze filters operate on the same principle but are more compact for personal use. The Sawyer has the benefit of fitting on more bottles and bags due to its common threading. The Katadyn isn't as versatile as far as containers are concerned but has a higher flow rate and is easy to clean in the field.

Chlorine dioxide drops or tablets should be carried for use if viruses are a risk or as a backup if your filter fails for some reason.

Recommended for International Travel

Grayl One Press Global plus chlorine dioxide treatment as a backup

This water bottle/press filter takes out bacteria, parasites, viruses, and many chemicals making it well suited for international travel where you don't know what you might run into. The weight and lack of capacity make it less than ideal for backcountry use in North America but make safe drinking water simple while travelling in countries with less reliable drinking water. If you are expecting to be on the road for an extended period of time bring a spare filter with you as the lifespan is only 250 liters (roughly 60 days at 4 liters per day).

And like the previous recommendations bring along chlorine dioxide drops or tablets to back up your filter in case of something malfunctioning.

What I use

My trips are all in North America in the backcountry or alpine environments. I use the Katadyn Befree for its ease of use, being lightweight, and high flow rate. I bring a spare Hydropak water bag in case the supplied squeeze bag gets punctured.

Additionally, I always have chlorine dioxide tablets from Katadyn in my kit for backup or treating water overnight as this gives long enough to kill cryptosporidium.


If you treat all water sources in the wild like they are contaminated you will greatly reduce your risk of contracting an illness.

As you can see there are a lot of ways to process safe drinking water. There are pros and cons to each so depending on what environment you are heading into you will have to decide what system is appropriate for the waterborne pathogens you will encounter.

Reliability, ease of use, and cost can all play a role in your decision.

Let us know in the comments what water disinfection approach you take?

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