9 Water Purification Methods for Survival

water purification methodsThe facts about water pollution in the U.S are scary:

At least 72 chemicals are found in an average cup of sea water. And about 46 % of the lakes and 40 % of the rivers are polluted.

In this post, I will show you 9 simple water purification methods you can use to make toxic and harmful water drinkable.

Each method is scored across a range of factors – including effectiveness, speed, and convenience.

Not only that, but I also show you the exact step-by-step process you need to follow for each method.

Let’s dive right in.

Download a free water purification checklist that includes all 9 techniques from this post, plus 2 additional methods (one of which has been proven to be just as effective as activated carbon).

Meet the enemies

There are three types of microorganisms in wilderness water that can affect you – bacteria, parasites, and viruses.

Here is a quick overview of the three threads:

Organism Examples Pore size Symptoms
Bacteria E.coli, cholerea, salmonella, Yersinis, etc. 0.2-0.5 microns Diarrherea, fever, nausea, vomitting
Parasites Giardia, Cryptosporidium, 2-15 microns Nausea, fatigue, cramps, fever, diarrherea, dehydration
Viruses Norwalk virus, Heptatitis A, rotavirus, polio 0.004-0.1 microns Vomiting, nausea, diarrherea, fever, cramps

Notice that viruses are extremely small compared to bacteria and parasites. This makes them almost impossible to remove with a traditional water filter.

In fact, the only way to inactivate viruses is through boiling, chemical treatment, distillation, and UV light (I will go over all these techniques below).

In addition to the three threads listed above, polluted water may contain heavy metals such as lead, cobber, and mercury.

Most water purification methods are not effective against toxic metals (not even boiling). However, I will show you a smart way to get rid of heavy metals later in the post (and in the exclusive bonus that is offered at the end).

What is the difference between a water filter and a water purifier?

Some people confuse these two terms. A water filter removes bacteria and parasites, but does not filter out viruses. A water purifier, on the other hand, removes everything – also viruses. A small but important difference.

Now it is time to walk you through the 9 water purification methods.

Method #1: Boiling

Effectiveness: Excellent Speed: Fair Convenience: Poor

Boiling is 100 % effective in killing bacteria, parasites, and viruses, making it a favorite among many survivalists and backpackers.

That said, bringing water to a rolling boil is not the most convenient method in the field.

It takes time – not only to set up, but also for the water to come to a boil – then cool off.

Boiling also requires a fuel source, which you may not have access to at the moment, and bad weather can make it difficult – or even impossible – to heat up the water.

For these reasons, you should never rely solely on boiling. Make sure to have at least one additional method of purifying water.

How long should you boil water?

If you don’t let the water boil long enough, it won’t be safe to drink. But how long is enough?

Well, according to EPA, the water should boil for at least 1 minute. At elevation over 5000 feet, it must boil for at least 3 minutes.

To be on the safe side, I always wait 5 minutes. I recommend you do the same.

Method #2: Chemical treatment

Effectiveness: Excellent Speed: Fair Convenience: Very good

While I am not a huge fan of chemicals, they can be extremely effective against harmful contaminants. In fact, the two most popular solutions on the market – chlorine and iodine – kill almost any contaminants that may be present in the water.

Chemical treatment tablets are also small, inexpensive, and have a long shelf life, which make them a perfect addition to your bug out bag.

That said, chemicals often leave the water with a bad and unpleasant taste and can take anywhere from 30 minutes to 4 hours to fully dissolve.

In other words, if you are in a hurry, consider using one of the other methods mentioned in this article.

As well, the effectiveness of the chemicals depends on several factors, including the temperature. As Princeton University puts it:

”The colder the water, the less effective the chemical is as a purifying agent. Research has shown that at 50 F (10 C), only 90 percent of Giardia cysts were inactivated after 30 minutes of exposure.”
Princeton University

The good news? There is a solution to all these problems. And I will reveal it in just a moment.

But right now you are probably wondering: ”How do I purify water with chemicals? What are the exact steps I need to take?”.

Good – glad to see you are asking questions. Let’s go over the two most popular chemical treatments – chlorine and iodine.

Option #1: Chlorine

There are basically two chlorine-based treatment options: Household bleach and chloride dioxide tablets.

Here are the primary differences between the two:

Household bleach Chloride dioxide tablets
Speed 30 minutes 4 hours
Effectivenss Kills most bacteria, parasites, and viruses, except from Cryptosporidium Kills all bacteria, parasites, and viruses, also Cryptosporidium
Shelf life 1 year if unopened and stored properly 4 years if unopened and stored properly

As you can see, household bleach yields quick results, but is not nearly as effective as chloride tablets. It also has a shorter shelf life.

Now, if you use chlorine tablets, follow the instructions on package to the letter – the chemicals themselves are poisonous.

If you use household bleach, follow these four steps:

Step #1: Add 2 drops of regular, unscented bleach per quart (liter) of water. If the water is cloudy or muddy, double the dosage.

Use this chart as a reference:

Volume of water Amount of bleach to add
1 quart/liter 2 drops
1 gallon 6 drops
2 gallons 12 drops
4 gallons 1/4 teaspoon
8 gallons 1/2 teaspoon

Source: US Environmental Protection Agency

Step #2: Stir and wait 30 minutes for the bleach to fully dissolve. For larger amounts of water (over 1 gallon), extend that to 2 hours.

If the temperature of the water is below 40 F (4 C), double these numbers – or heat up the water first.

Step #3: If the chlorine taste is too strong, add 50mg of vitamin C or a pinch of salt per quart (liter), and you should be good to go.

And guess what?

That’s basically all there is to it.

Option #2: Iodine

Iodine is just as effective as household bleach. But again, it doesn’t kill the dreaded Cryptosporidium parasite which can cause both diarrhea, fever, and stomach pain.

On top of that, some people are allergic to iodine. Pregnant women (and people with thyroid problems in particular) should avoid it altogether – or consult a doctor before use.

The process of purifying water with iodine is almost identical to that of household bleach. Except for one thing: You should not add 2 drops of the chemical per quart (liter) of water, but 3-5 drops (assuming that you are using a 2 % iodine solution).

Simple, right?

Method #3: Distilling salt water and urine

Effectiveness: Excellent Speed: Poor Convenience: Poor

Distillation is extremely effective. It will remove both bacteria, parasites, and viruses. Heck, it will even get rid of heavy metals like lead, arsenic, and mercury.

That’s also why it is used extensively in developing countries that must work with heavily contaminated water.

It is also the only water purification method that can make salt water and urine drinkable.

But despite these benefits, distillation is not flawless. The process is very slow and only provides 1 liter of clean, drinkable water for every 5 liter of contaminated water you purify.

Distillation is not very convenient in the field either. You need a lot of equipment – including a heat source, a pot with a lid, and a cup. If you are headed out of or through a disaster zone, it is unlikely that you will have all these items at hand.

That said, if you have the time and resources, this can be a powerful and reliable way to treat the water.

Here is how it works.

Step #1: Place the cup directly in the center of the pot

Step #2: Fill the pot halfway up with water or urine (add too much water and it will splash in the cup when boiling).

Step #3: Place the lid upside down over the pot and allow the water to come to a slow boil.

And that’s it. The water will now condense on the (inverted) lit and run back down into the cup in the middle – fresh, clean, and ready to drink.

Method #4: Using commercial water filters

Effectiveness: Good Speed: Excellent Convenience: Excellent

Commercial water filters are usually not as effective as boiling, chemical treatment, and distillation.

They will remove bacteria and parasites, including Cryptosporidium and Giarda, but not viruses. Why? Because viruses are too small to be filtered out.

With that said, some filters contain a chemical component – usually an iodine disinfectant – that kill viruses.

On top of that, many water filters are small, lightweight, and easy to carry, making them an excellent option in a bug out scenario.

The question is: What should you look for in a commercial water filter?

In my opinion, there are four factors you need to consider.

Factor #1: Weight

There is no two ways about it. If you want to keep pack weight to a minimum, a small, lightweight water filter is a must.

As a general rule, look for anything below 8 ounces.

Luckily, many solutions on the market are designed specifically with backpackers and outdoor enthusiasts in mind. So this shouldn’t be difficult to find.

Factor #2: Effectiveness

The effectiveness of a water filter can be measured by its absolute pore size. The smaller the pore size, the cleaner the filtered water will be.

CDC (Centers for Disease Control and Prevention), recommends a pore size of 1 micron or less.

This means that microorganisms 1 micron or larger won’t be able to pass through the filter.

Factor #3: Durability

If you want your water filter to last for a long time (and who doesn’t?), it must be able to handle a lot of water.

As a rough guideline, look for a filter that can handle at least 1000 gallons (3.785 liters) before it needs to be replaced.

This should be easy to find. Many filters are made specifically for survival and emergency use.

Factor #4: Price

This may or may not be important to you. As with anything else, quality and price usually goes hand in hand.

You can easily find a water filter that meets the criteria above for $50 or less. But if you want a chemical component included, you will have to pony up $100 or more.

The Sawyer Mini Water Filter

Want a high-quality water filter that is incredible effective, easy to drink from and weighs next to nothing? Then I highly recommend the Sawyer Mini water filter.

The Sawyer Mini is so small that it fits in the palm of your hands. It has a pore size of only 0.1 micron (which is 10X better than the recommendation from CDC) and can filter 100,000 gallons of water before it needs to be replaced.

Not too shabby.

You can check out the Sawyer mini water filter here

Method #5: Improvising filters

Effectiveness: Fair Speed: Poor Convenience: Poor

It goes without saying that an improvised water filter isn’t nearly as effective as a commercial solution.

It removes some bacteria and parasites, but not them all. And that’s why you should only use it as a last resort (if everything else fails) or as a precursor to chemical treatment or boiling.

Building an improvised filter is also a time-consuming process. You need to find all the materials, build the filter, and then treat the water – preferably multiple times to be on the safe side.

Here is a simple way to make your own water filter.

Step #1: Cut off the bottom of a plastic bottle and make a small hole in the cap, so the filtered water can run out.

Step #2: Place progressive layers of charcoal, sand, rocks, and grass (in that order).

Charcoal neutralizes toxins, remove sediments, and improve taste. Sand and gravel filter out smaller particles, and grass prevents larger particles from passing through.

As another barrier, you can put your t-shirt, a bandana, or something similar over the end of the bottle. That way the filter becomes even more effective.

Step #3: When you have built your filter, all there is left to do is pour water through it. Repeat several times for best results.

Note: You don’t necessary need a bottle for this method to work. You can just as well use a pair of socks, some latex tubing, or a plastic bag.

What makes the filter effective is the different layers of grass, sand, and charcoal, not the container itself.

Similarly, you may not be able to find all the materials you need, and that’s okay. Use what you have and improvise as much as you can.

Method#6: Digging a seepage basin

Effectiveness: Fair Speed: Very good Convenience: Fair

This method is great if you don’t have any resources or equipment available. It can be done in 5-10 minutes and requires no experience or expertise whatsoever.

On the flip side, digging a seepage basin does not guarantee that the filtered water is 100 % clean. Like an improvised filter, it will remove some bacteria and parasites, but preventing them all from passing through is near impossible.

If you decide to dig a seepage basin, follow this simple, three-step process.

Step #1: Find a water source. As a rule of thumb, water from rivers and streams is safer than water from standing sources like ponds and lakes.

Step #2: Dig a hole 2-4 feet from the water source. The hole should be about 3-5 feet in diameter.

Step #3: Wait. The soil between the hole and the water source will act as a natural filter, and you should see the hole slowly begin to fill with fresh, drinking water.

Method #7: Solar water purification (SODIS)

Effectiveness: Excellent Speed: Poor Convenience: Poor

This is a long-term favorite of mine. It is simple, requires no equipment at all, and leaves the water 100 % free of harmful microorganisms (study, study).

However, it takes a lot of time – anywhere from 6 hours to 2 days depending on the quality of the water and the current weather conditions.

Another thing you have to keep in mind is that it only works with smaller amounts of water (less than three liters).

On top of that, the water must be clear. If it is cloudy or muddy, use another water purification method.

Here is the step-by-step process:

Step #1: Fill a container with water. The container must be transparent and colorless. Green or brown bottles are not going to work.

Step #2: Leave it in the sun for at least six hours. In cloudy weather, let it sit for two days.

And that’s basically all there is to it. The ultraviolet light will now kill all bacteria, parasites, and viruses.

Method #8: Create a solar still

Effectiveness: Excellent Speed: Poor Convenience: Fair

There is no other way to say this: Creating a solar still is one of the most effective methods of water purification in existence.

Not only does it remove bacteria, parasites, and viruses. It also eliminates heavy metals like cobber and mercury.

At the same time, a solar still can be used to distill salt water and urine, making it an extremely powerful method of treating water.

The biggest problem with a solar still, however, is that it requires a lot of time. In fact, it only produces one quart (liter) of water per day.

But if you have plenty of time, a solar still will provide you with fresh, clean water day in and day out. You set it up once and let it work for you as long as needed.

Here is how to create your own solar still.

Step #1: Dig a pit. It should be around 1½ feet deep and 3 feet in diameter.

Step #2: Cover the pit with fresh vegetation. Avoid poisonous plants. They will only produce poisonous water.

Step #3: Place an empty container in the center of the pit, on top of the vegetation. This will be your collection point.

Step #4: Cover the hole with transparent plastic, seal the perimeter with sand and place a stone in the middle.

Step #5: Leave it overnight. Water from the ground and vegetation will now evaporate and condense on the plastic sheet and run down into the container.

As you may have noticed, this method works even if you have no water available. That’s why it is well suited for the desert.

Distilling salt water or urine

If you want to use the solar still to distill salt water or urine, simply pour it over the vegetation in step 2. Then follow the rest of the process as you normally would.

Now, it is time to discuss the final water purification technique.

Method #9: The banana peel trick

Effectiveness: Poor Speed: Fair Convenience: Fair

So you are probably thinking: ”Can banana peels be used to purify water?”

Well, um… kinda.

In a Brazilian study, researchers found that banana peels are incredible effective in removing toxic metals like lead, nickel, and cobber.

But that’s also about it. The banana peel method does not eliminate bacteria or other microorganisms in the water. Only heavy metals.

And that’s why you should always combine it with another water purification method such as boiling or chemical treatment.

That way, you will be left with 100 % clean, drinkable water. No bacteria, no parasites, no viruses, and no toxic metals.

But keep in mind: This process is time-consuming. Expect to set aside at least three hours.

Here are the exact steps you need to follow:

Step #1: Let the banana peels dry in the sun for a few hours.

Step #2: Cut the peels into smaller pieces

Step #3: And finally, toss the banana chunks into the water and let it sit for about an hour. The banana peels will now absorb up to 97 % of the toxic metals in the water.

Can you reuse the banana peels?

Yes. In fact, according to the Brazilian study, you can reuse the banana peels up to 11 times before they lose their antioxidant qualities.

Not bad.

Final words

As you can see, there is no perfect water purification method that works in any condition. They all their pros and cons. And that’s why it is a good idea to master them all.

To help you get started I have created a checklist that shows you how to implement all 9 strategies and techniques from this post.

The checklist also includes two additional methods of purifying water – one of which can be used to remove toxic metals from the water in just a few minutes.

You can download the checklist below.

Download a free water purification checklist that summarizes this guide

  • Includes all the tips and tricks from this post, plus 2 bonus methods that no one in the survival community is talking about
  • Easily print or save as a PDF for quick and easy reference when you want to practice the techniques.