How to Filter Water Outdoors When You’re in a Pinch

You’re out camping and running low on water, and you see a clear-looking stream that looks appealing. Before you dip your cup into that water, though, you might ask yourself if it is worth getting sick over.

Unless you’re prepared to filter or purify that water, you might pay later for every sip you take. We’ll teach you a few ways to ensure the water you’re drinking in the wilderness doesn’t do your body more harm than good.

Table of Contents

    Why Filter/Purify Water Outdoors

    Just because the water you see in lakes, streams, or beaches looks clear and healthy, doesn’t mean it is.

    You’d need a microscope to see the bacteria and microorganisms that lurk in that seemingly clear water.

    Sometimes, ingesting even a small amount of contaminated water can make you extremely sick. Here are some organisms that can be found in drinking water and just how dangerous they are.

    1. Giardia: Humans commonly become infected with this microscopic parasite via drinking water from lakes, streams, or water that hasn’t been properly treated (1). The symptoms aren’t pleasant — they include nausea, stomach cramps and pains, gas, diarrhea, and dehydration. Since this protozoan is fairly big, it can be filtered out of water.
    2. E. coli: This kind of bacteria can be extracted from water by using water filters. If you’ve ever had or heard of traveler’s diarrhea, you can thank this bad boy for that. Another strain can cause extremely severe diarrhea and can even be fatal (2).
    3. Campylobacter: You’ll typically be able to handle this bacteria spread through contaminated water or undercooked poultry on your own, but you may need medical intervention in some cases. That doesn’t mean it’s a walk in the park, though. Expect bloody diarrhea, stomach cramps, and fever (3).

    Filtering vs. Purifying

    Although you may hear people use these terms interchangeably, filtering and purification are not the same when it comes to decontaminating water.

    While both are better than doing nothing at all, water purifiers provide the most protection.

    A filter uses a physical barrier, such as charcoal, to take the undesirables out of the water. When filtering water, you’ll remove bacteria and protozoa if you use the right filter.

    Ideally, you’ll have a filter with an absolute pore size of 1 micron or less. That will be highly effective in giardia and cryptosporidium removal (4). What you won’t be able to take out of your drinking water with this method, however, is viruses.

    When you purify water, you’re also working to remove the bad stuff. But you’re doing so by using chemical methods, such as adding chlorine or iodine. When you purify water, you can remove bacteria and protozoa, but you’ll also get rid of the viruses that are too tiny to be removed by your filter (5).

    As a rule, purifying is the way to go. But if you don’t have the chemicals you need while camping and you’re becoming dehydrated, it’s better to use filtration than nothing at all.

    Methods of Filtering and Purifying

    There are so many methods of filtering and purifying water that it can become confusing trying to decide on one and how to be sure you’re doing it correctly.

    Let’s take a closer look at the most popular methods.

    1. Boiling

    If you’re caught without any safe drinking water in the wilderness, boiling is an easy method you can use. You won’t need any special tools and it’s free to do. All you need is a container and the ability to start a fire.

    To boil it, put the water in a heat-safe pan or container. Put it over an open flame or camping stove. Once it’s reached a rolling boil, you’ll have to maintain that boiling for at least one minute (6).

    If you are at a higher altitude, at one mile or higher, you’ll need to boil your water for at least three minutes instead of one. This will kill bacteria, giardia, and cryptosporidia.

    Keep in mind, if the water is cloudy, you should also filter it before drinking to remove the larger particles and make the water safer. To filter, pour the water through something like a coffee filter or clean cloths.

    PROS:
    • Cheap.
    • Easy to do.
    • Effective in eliminating harmful organisms.
    CONS:
    • It won’t take care of chemical pollutants or heavy metals.
    • You will have to wait for the water to cool before drinking.
    • It can be time-intensive to boil enough water for several people.

    2. Chemical

    For chemical purification methods, cloudy water will require more chemicals to disinfect. And if the water has fairly big particles in it, filtering is recommended first because the particles may not be fully purified after treatment. Only the outside of the particle might be treated.

    Iodine

    Starting with a clean container, try to remove the water from areas in which you see animals. When possible, try to get your water from moving sources, such as streams. If you have to take water from a lake, aim for as near the surface as possible.

    After you’ve collected your water and filtered it, you should use an iodine tincture of 2 percent iodine and 47 percent alcohol. You can also try tablets. If you use a tincture, you’ll also want an eyedropper so you can be precise with your measurements (7).

    You should put 5 to 10 drops in the container for every one liter of water. How do you know whether to put more or fewer drops?

    If the water source is still or cloudy, like a lake, use around 10. If the water looks clear and comes from a moving source like a stream, you can opt for less iodine.

    After adding the iodine, wait five minutes. Then take your water bottle or cup and purify the rim and mouth of the cup by swishing the iodine water on it. Then wait for about another 30 minutes.

    PROS:
    • Cheap.
    • Lightweight to carry.
    CONS:
    • The flavor isn’t great.
    • Not recommended for kids, pregnant women or people with thyroid issues.
    • Too much iodine can be toxic.
    • Won’t take care of parasites.

    Chlorine-Based Disinfection

    Chlorine can be used to disinfect drinking water when you’re in an emergency situation. To use this method, add one teaspoon of plain liquid bleach, which includes the active ingredient sodium hypochlorite, to one gallon of clear water. If the water is cloudy, use two teaspoons per gallon (8).

    Wait 30 minutes and then give your water a sniff test. If you smell chlorine, you’re good to go. If you don’t smell anything, repeat the process of adding chlorine in the same quantity until you can smell it after waiting 30 minutes.

    You can also use chlorine dioxide tablets, which would be easier to carry than a jug of bleach during a camping trip. For many of these tablets, you’ll use one per quart of water.

    PROS:
    • Kills bacteria, giardia, and viruses.
    • It doesn’t take much backpack room to carry a box of tablets.
    • It can improve the taste of water.
    CONS:
    • Pricier than boiling.
    • It won’t treat chemicals.

    Tablets and Drops

    You can use iodine and chlorine in both tablets and drop form, but there are other agents used to treat water as well.

    Another active ingredient used in water purification is sulfate mineral salts. After you add the salts, you have to wait 60 minutes until you can drink the water. Follow the directions on the packaging when figuring how much to add to your water.

    PROS:
    • Works on giardia, viruses, and bacteria.
    • No chemical taste.
    • Will also eliminate or reduce heavy metals.
    • When stored correctly, it has an unlimited shelf life.
    CONS:
    • It doesn’t work on cryptosporidium.
    • Fairly pricey compared to other methods.
    • Longer waiting time before being able to drink the water.

    Do-It-Yourself

    Steam Distillation

    If you want extremely pure water, steam distillation may be your best bet. It removes biological, radioactive, organic, and inorganic substances. Since steam water distillation involves extensive boiling, it kills parasites, viruses, and bacteria.

    To do steam distillation, you’ll boil water in a container and trap the steam. You’ll have another container connected to that first one and it will collect the condensed steam created from the boiling process. After you’ve boiled all the water from the first container, you’ll have purified water in the second container (9).

    Here’s how you do it:

    1. Get all your equipment together. You’ll need a metal kettle, stainless steel funnel big enough to fit on top of the kettle, coiled tubing, a big bucket with a hole near the bottom in the side for the tubing, a jar, heat, cornmeal, flour, and ice.
    2. Place your kettle on your heating source and put the funnel on top of it, upside down.
    3. Grab your tube and attach it to the smallest area of the funnel.
    4. Coil the tube around in a circle, much like a Slinky. You’ll want about three feet of coil between the funnel and your bucket. You’ll coil the tube inside the bucket and then pull the end of the tube outside the hole in the bucket.
    5. Put your jar underneath the part of the tube that is coming out of the bucket.
    6. Put ice in the bucket.
    7. If necessary, make a half and half mixture of flour and cornmeal and create a paste out of it by adding a little water. You’ll use that dough to seal up cracks or space between the tubing and funnel and other areas. Let that paste dry for several hours.
    8. Put the water you want to purify in the kettle and turn on the heat.
    9. As the steam is formed, it will force its way through the tubing. When it hits the cold area in the bucket from the ice, it condenses and turns back into water.

    You can also use a kit that’s more involved and comes with a cooling coil.

    PROS:
    • It creates extremely pure water.
    • Inexpensive if you’re doing it outside with a homemade system.
    CONS:
    • It can take hours to produce one gallon of water.
    • It can be expensive if you buy a steam distiller kit.
    • It takes a fair amount of set-up and resources.

    Sand/Charcoal Filtration

    If you find yourself outside needing drinking water, you can create a sand/charcoal filter. There are several variations of sand filters, including the basic one we’ll describe below. In the more advanced models, additional filtration takes place on top of the sand in a biolayer that contains an ecosystem that will kill the viruses and other organisms.

    The sand is helpful for stopping bigger organisms from traveling through, keeping it away from the filtered water.

    Activated charcoal is a natural filter that adsorbs toxins and other organics from water. As a result, it makes your water taste better (10). If you have access to a campfire and have created a good coal bed, this will serve as a good source.

    Here’s how to make your own:

    1. Get a two-liter bottle and cut four inches off the bottom.
    2. Take off the bottle cap and put a coffee filter on the outside of the neck, securing it with a thick rubber band.
    3. Take another two-liter bottle and cut approximately four inches off the top of it, not the bottom this time.
    4. Take the coffee filter bottle, turn it upside down, and place it filter first into the second bottle.
    5. Crush the charcoal into powder and add it to the filter as a first layer.
    6. Collect gravel and put it into the top bottle. It won’t drop through because of the coffee filter.
    7. On top of the gravel, add a layer of coarse sand. On top of that, add finer-grain sand.
    8. Slowly pour the water on top of the sand and gravel mixture.
    9. The water that drops into the lower bottle should be clean.
    PROS:
    • Cheap.
    • Easy to maintain.
    • Don’t need a lot of space.
    CONS:
    • It doesn’t filter out heavy metals and chemicals.
    • The filtering process can be quite slow.

    Wood and Tubing

    The wood and tubing method of filtering is surprisingly effective at taking bacteria out of the water — as much as 99 percent can be removed.

    To get started, you’ll want to cut a piece of sapwood that is about two inches in length and approximately an inch wide. You’ll need plastic tubing to tightly fit over the piece of wood. If it’s loosely fitting, you can cinch a clamp around the area where the bottom of the tubing and the wood piece meet.

    You’ll pour water into the top of the tube and put the bottom of the tube into a cup or other container. The water will filter through the piece of wood, which is why you need the plastic to fit tightly over the wood: so untreated water doesn’t sneak through along with the filtered water.

    PROS:
    • Easy to do.
    • Extremely cheap.
    • Removes most bacteria.
    CONS:
    • Slow to filter the water — it will take all day to filter approximately four liters of water.
    • You’ll have to keep an eye on it to refill the tube with more water when it gets low.

    Hydrogen Peroxide

    This isn’t the best method for purifying water, but it will rid water of iron and hydrogen sulfide. It works best when used in conjunction with dry chlorine. The chlorine will kill additional contaminants in the water, and the hydrogen peroxide gets rid of the chlorine flavor left behind.

    You’ll add two milliliters of household hydrogen peroxide per gallon of water. You must let the water sit for at least 15 minutes before you drink it.

    Caution

    Hydrogen peroxide is available in stores at different concentrations. Household grade contains 3% hydrogen peroxide and is usually not dangerous to ingest at small amounts. However, higher concentrations should never be taken orally (11).
    PROS:
    • Inexpensive.
    • Easy to do.
    • Quick method of treatment.
    CONS:
    • Not the most effective treatment method — other ways remove more undesirables from water.

    Sedimentation

    With sedimentation, you would collect water from your source, place it in a container, and leave it alone to settle. After you see the sediment has sunk to the bottom, you carefully pour the top layer of clear water into another container.

    This method will remove the larger particles from your drinking water, but just because it appears clear doesn’t mean it’s healthy to drink. It’s fine to use this method, but you should do it in conjunction with another method, such as boiling, filtering, or a chemical treatment, to kill off the hazardous materials in the water.

    PROS:
    • A free way to remove debris from water.
    • The larger particles sink to the bottom pretty quickly.
    • It’s a great way to remove the cloudiness from water.
    • No equipment needed, other than two containers.
    CONS:
    • You’ll have to use another purification method in conjunction.

    Cloth Filtration

    Before drinking water from a lake or stream in the wilderness, it’s a good idea to do basic filtering of your water by using a cloth. You can use anything you have handy — a spare shirt, a towel, or a blanket. Start by wetting the fabric.

    There are two methods you can use. If you’re in a hurry for water because you’re dehydrated, take the wet fabric, and double over your cloth to make two layers.

    Put your cloth over your container, keeping a bit of the fabric hanging loosely in your container to create a small reservoir for the water.

    Slowly pour the water onto the fabric, taking care not to pour more than the fabric can drain. You don’t want to lose the water you’ve just collected by pouring too quickly. The fabric will strain out some of the impurities that are too big to pass through the fabric.

    You should use a fabric that is tightly woven or knit to ensure you’re catching as many particles as possible.

    If you have more time on your hands, a more thorough cloth filtration method involves taking that wet piece of cloth and placing one end of it in the dirty container of water. Then you’ll set your empty container for your clean water next to the other one, close enough that you can place the other end of the fabric in the empty container.

    You’ll want to place that empty container a little lower than the other one. Drip by drip, thanks to gravity, that water will move to the empty container.

    PROS:
    • It’s a free way of removing some impurities.
    • You don’t need any special equipment.
    • You don’t need to use any energy, like heat, to do it.
    CONS:
    • It won’t remove smaller particles from your water, which means you might still get sick.

    Commercial Filters

    Survival Straw

    Survival straws are touted as a handy, potentially lifesaving tools to have on your wilderness treks. It’s a small and lightweight water filter you can use, by putting it directly into your water source and simply sipping.

    The hollow fiber membrane in these straws can filter up to 1,000 gallons, which would supply you with more than enough water when you’re outside. It strips away virtually all protozoa, parasites, bacteria, and even microplastics.

    To use it, you’ll open the caps on both ends and prime the filter by sticking the non-drinking end of the straw in the water for 10 seconds. Take a couple sips to get the water moving through the straw. Then you can drink as much as you need through the straw.

    When you’re done, you’ll blow the excess water out of the end of the straw and put the caps back on.

    PROS:
    • Removes virtually all bacteria, parasites, and microplastics.
    • Doesn’t take up much room in your backpack.
    • Is quick and easy to use.
    • Only weighs 2 ounces.
    • Improves the water flavor.
    CONS:
    • Doesn’t remove viruses from water.
    • It’s hard to suck water through the straw.
    • Since the straw has to be held close to the water source, you’ll either have to collect it in a cup or lay on the ground to use.
    • Clogs easy.

    UV Water Filtration

    If you like the idea of harnessing technology to make your water safe, you can opt for a UV water filtration system. With this method, artificial UV light will be used to kill bacteria, protozoa, and viruses. It works in seconds.

    With the SteriPen, one brand of UV light purifier available, you’ll collect a liter of water, stick the light in the water, and stir it around for 90 seconds.

    PROS:
    • Doesn’t use any chemicals.
    • Works quickly.
    • Light and easy to carry.
    • No undesirable taste.
    CONS:
    • Expensive initially.
    • Can’t fully penetrate bigger particles so filtering is also recommended.
    • Requires energy.

    Filtration Water Bottles

    With filtration bottles like BeFree, all you do is fill your bottle, put on the lid, shake to filter the water, and drink.

    With a .1 micron water filter, it will take 99.99 percent of bacteria and protozoa out of your water. One bottle can filter as much as 1,000 liters.

    PROS:
    • So easy that anyone can do it.
    • Super fast way to filter water.
    • The bottle is lightweight.
    • The bottle is soft so it folds into compact places.
    CONS:
    • The soft flask is great for packing, but can tear.
    • Since it is soft, it won’t stand up on its own.
    • Some people complain of a plastic taste.
    Learn More
    portable water filterBest Portable Water Filters of 2020

    Activated Carbon Filter Pumps

    You place the pump part into the container of dirty, contaminated water. You’d place the other tube of the pump into a clean container. Pump the handle up and down and let the carbon filter do all the water purification for you.

    There are several of these pumps on the market. The Purewell pump is capable of outputting 58 ounces of water per minute. You can get 793 gallons of water from the pump before having to switch out the carbon filter.

    PROS:
    • Easy to use.
    • Inexpensive for all the gallons you get.
    • Lightweight to carry.
    • Improves the taste of the water.
    CONS:
    • It can be a two-man job to operate until you get the hang of it because it can slip and slide around.

    Solar Water Purification

    You can purify drinking water using solar methods.

    Two ways of using solar energy for improving water include solar distillation and solar water disinfection.

    Solar distillation uses a closed system to cause the evaporation of water. Then, the condensation is collected. This can be a useful way to remove salt from ocean water.

    Solar disinfection by contrast uses the sun’s power to render organisms, such as bacteria, protozoa, and viruses, harmless. This is the preferable method for disinfecting water because of its high success rate.

    To use solar power to disinfect your water, find the clearest water you can. If you can’t get clear water, you could use the sedimentation method or a filter to improve it.

    Fill plastic soda bottles with the water and shake to disperse oxygen throughout. Put the bottles in a sunny spot, such as a roof. Let the light hit them for at least six hours on a sunny day.

    If the sky is cloudy, you should let the bottles sit for two days (12).

    PROS:
    • The sun is a free resource for everyone.
    • Most people have access to plastic bottles.
    • It doesn’t change the flavor of the water.
    CONS:
    • You may need to filter the water as well.
    • It can take up to two days before your water is ready for consumption.

    Best Methods for Different Scenarios

    With so many methods available, how do you know which one is best for you? The best one may depend on your surroundings and what you’re trying to achieve.

    Let’s look at three common situations and discuss which method may suit which circumstances.

    Traveling/Hiking

    While on the go, you don’t want to waste a lot of time making sure you have clean water. You want to see the sites and cram as much into your trip as possible. That’s where UV light treatment shines.

    You can get your water clean quickly. But remember, you need to filter that water first, so bring a coffee filter with you for a lightweight and cheap way to get the bigger particles out. Filtering is always a good idea, but it’s especially important in third-world nations or when you’re traveling internationally.

    One word of caution about UV light treatment: some of the commercial UV light treatment products tend to quit working unexpectedly, so you might want to have a back-up with you. Plus, if you have two of them, your travel companion can treat their water at the same time you do so you can get back on the move.

    Camping

    When camping, you’ll often have access to fire rings, or you can easily set up your own. You’ll likely have a lighter or matches packed or even some fire starters. For that reason, boiling is a great option when you’re camping.

    Since boiling won’t remove particles or dirt, however, you might also want to filter your water first. You could remove the particles quickly with a cloth filter or use the sedimentation method as you set up your tent.

    If you are using charcoal to build a campfire, then a charcoal filter would be the most practical and efficient filtration method.

    Survival

    When you’re in survival mode, you may not have commercial products with you and you don’t want to chance them failing when your life may depend on it. If you have a way to light a fire, boiling is always a good bet. It’s an effective, cheap, and straightforward process.

    If, for some reason, you can’t boil, a wood tubing filter is another option — it’s easy to do and you won’t have to worry about high-tech equipment failing you or running out of chemical purification tablets or drops.


    Frequently Asked Questions

    Should you treat your water?

    All water you collect outside should be treated as potentially contaminated and should be treated. Although it may look clear, harmful organisms could be lurking unseen. Drinking even a few sips of such water could make you extremely ill.

    For that reason, and with so many effective and easy ways to treat water, you should never drink untreated water unless it’s a true emergency. Even then, you should be able to do some sort of treatment, even if it’s just taking off your shirt and using it as a filter. That’s still better than doing nothing at all!

    Can I use the Brita filter to purify water?

    Brita water filters can be a good idea for your home. They do take away some potentially harmful contaminants such as copper, lead, chlorine, and pesticides. What’s more, plenty of people think Brita filters improve the taste of their water.

    In the outdoor setting, however, you shouldn’t rely on a Brita filter because they won’t kill bacteria or microorganisms (13). That means if you use this product instead of another water purification method, you may still become ill because of tainted water.

    Is it okay to rely on one method while in the wilderness or camping?

    It’s best to always have at least two methods of purifying or filtering water when you’re outside. Let’s say you pack matches so you can boil water, and that’s the only method you plan on using. What happens if those matches get wet in a rainstorm or you lose them?

    Unless you have back-up method in mind, you’ll be out of luck.

    Is it safe to drink rainwater?

    Multiple factors influence whether rainwater is safe to drink. One factor is the atmosphere it passes through. If you’re in a city where there is air pollution, harmful particles may find their way into your rainwater (14).

    The collection system used to gather the rainwater also plays a role in how safe it is to drink. If you collect the rainwater from rooftops, you may be drinking bacteria left behind by bird droppings.

    If you’re determined to drink rainwater or you have no other water source available to you at the moment, your best bet is to boil it for at least one minute before drinking it. If you’re in areas of higher elevation, boil it for three minutes.

    What is the safest way to purify water?

    Boiling is still the gold standard when it comes to purifying water. It’s easy to do and there’s little room for error. You can do it anywhere as long as you have access to a heat source.

    It can take some time, especially waiting for the water to cool, but it reliably kills the harmful organisms you’ll encounter.


    Sip with Safety

    It’s scary how your water can look perfectly clear yet still make you sick. And it can be overwhelming to pick the best method of water filtering or purification when the stakes are so high.

    When going out on a trip preparation is key to staying safe. Armed with knowledge and a few simple tools and materials, you’ll ensure you enjoy your time outdoors without fear of becoming a statistic.

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