How To Purify Water – Water Purification Process

How To Purify Water – Water Purification Process

“Water, water everywhere and not a drop to drink,” as the old saying goes. A more apt statement for these times might be, “water, water everywhere, but is it safe to drink?” And if it’s not, what is a reliable water purification process?

Sadly, in this day and age there are few, if any, places where the water is safe to drink without treating, no matter how pristine and inviting it may look.

Water in the wild often contains harmful microorganisms, bacteria and parasites that can cause a variety of ailments, such as giardia, dysentery, hepatitis, and hookworms. Luckily, however, we’re going to learn a few simple ways how to purify water to make it safe for consumption.

I. How to Purify Water — Water Purification Process: boiling

The simplest method to purify water is probably boiling.

You need to bring the water to a full, rolling boil for at least five minutes to be safe, with some experts recommending an even longer time. The down side to boiling your drinking water is that it removes the oxygen and the water ends up tasting flat. You can improve its quality by pouring it back and forth between two containers to put oxygen back in, or simply shake it up.

II. Water Purification Process: purifiers

There are also several chemical purifiers on the market. Iodine comes in either liquid form, (which can be messy), or tablet form.

One to two tablets or drops will clear up a quart of water.  Shake your water bottle or container and wait twenty minutes before drinking. Water treated with iodine will have a darker color and a bit of an unpleasant flavor.

It is possible to mask this flavor by adding a powdered drink mix, but be sure to wait the twenty minutes before adding it, as it will interfere with the iodine’s effectiveness.

Other chemical treatments to purify water that work similarly to iodine are chlorine tablets, potassium permanganate, or halazone tablets. You should be able to pick these up fairly cheaply at most outdoor stores.

You can even add a few drops of bleach in a pinch, though I wouldn’t recommend overusing this one. It is important when using chemical purification to make sure all surfaces have been decontaminated.

After waiting the twenty minutes, slightly unscrew the lid of your water bottle or container and rinse around the threads and lid. The nice thing about using tablets is the container is very small and portable and can be slipped into a pocket, a plus if you do not want to carry a stove or pot, or take the time to boil water. Chemical treatment can be done on the hoof with minimal stopping time.

III. Water Purification Process: filters

A third method of treatment is commercial filters. These come in all shapes, sizes and price ranges. Most work by pushing the water through a charcoal or ceramic filter and then chemically treating it. Normally, they have one hose with a float that goes from the water source to the filter and a second hose, for clean water, that goes from filter to water bottle. When using this type of filter it is important to not cross contaminate the hoses. Keep the clean hose in a separate plastic bag so it never touches the contaminated hose. The plus side to this method of how to purify water is that there is no flat or funky flavor. Commercial filters are also good for when the water is on the murky or dirty side, as they will remove this also. The drawback is that the sediment or tannins that you are filtering out will quickly clog up the filter. Some can be cleaned, with others you need to buy a replacement filter. Like all technical equipment, cost and breakage are things to be considered.

IV. Water Purification Process: primitive methods

Beyond these common methods, there are more primitive techniques for the serious survivalists (or the unlucky person who was caught unprepared).

One is filtering through soil or, preferably, sand. Keep rinsing the water repeatedly through the sand until it is looking clear. A variation of this is to dig a hole near where the source is and use the water that filters through into the hole. Be aware, that although soil is a good filter for sediment and other particles, it is not a guarantee for things like bacteria. This is even true for spring water, which many people assume is safe to drink without treatment.

Distilling is a method that can be used for either collecting water or gathering fresh water out of salt water.

To collect water from the ground, dig a deep hole and place a collecting container or water bottle in the center.

Cover the hole with a clear sheet of plastic. The plastic needs to be weighted in the center with a rock or heavy object so that it points down into the container.

Then, secure the sides of the plastic tightly around the hole, such as by covering with dirt. The clear plastic acts like a greenhouse. The water in the soil evaporates as it heats up. When it hits the plastic it runs down to the point and drips off into the container. If all you have is salt water, you can distill it by placing a small pot inside a larger pot. The salty water goes in the larger pot but not the smaller one.

Invert a lid over the pots that will point down into the smaller pot, then bring the water to a boil. As the water boils, fresh water will evaporate, hit the lid and drip down into the smaller pot, leaving the salt, or other minerals behind.

An alternative if you don’t have a smaller pot is to put a cloth over the pot the will absorb the steam. Use caution when removing it to wring it out so you don’t get burned.

For another primitive method of how to purify water, see our article on Boiling Water with Stones.

Above all, be cautious and use common sense when choosing where to gather your water.

Do the plants surrounding it look healthy?

Are there dead animals near by that might have contaminated it?

Don’t collect any water that looks stagnant. Generally, water that is further upstream will be cleaner than that downstream, but there are no guarantees.

Don’t automatically go for the fasting rushing water, as fast water carries more sediment. You can avoid picking up a lot of sediment by making sure you dunk your water bottle completely under the water. This will avoid all the dirt and debris that floats on the surface.

With so many ways to purify water, there should be something for everyone and no reason to ever take chances drinking untreated water.

There are die-hards out there who will argue that the risk is small and not worth worrying about. But a nasty case of beaver fever in the back country can be not only uncomfortable, but life threatening.

Diarrhea and vomiting can cause serious dehydration and sap your strength to the point that you can get yourself to safety.

If you are going to spend time in the outdoors, always make sure you have at least one, if not two or more, methods for purifying water. It’s vital to know water purification process methods. Make sure you view our Giardia article to be aware of the hazards of water that has not been purified.


Cathy Ellis is a teacher at Adirondack Wilderness Challenge, a wilderness adventure program for court adjudicated youth.


  1. Joe Wilkerson

    Good article. While I am not a survivalist, I do believe in being prepared, especially in this day and time. I think the world as we know it is about to change to the point us not recognizing it. I want to at least have water to drink and something to eat be it meager or not. Thank you again.

  2. Todd Martin

    Hello I am also a teacher of wilderness survival and I would like to make a couple of changes if I could. According to recent findings Iodine is one of the things that you do not want to use to purify water and here are the reasons why. one if you have anyone in your group that is allergic to shellfish then you will also have a medical emergency on your hands from the iodine, secondly Iodine and chlorine have been found not effective against cryptosperidium which besides guardia are the 2 biggest bugs in the water infesting 97% of all waters in the US. so if it is not effective against one of the 2 biggest bugs then don’t use it. there are other alternatives like sodium hypochlorite and chlorine dioxide which are found in MSR micropur tablets and aquapure tablets. these are effective as a full purification tablet but remember to read the instructions as clarity and temperature of the water will effect purification times with a min. of 30 min. to 4 hours. more to come later thanks for reading.

    • What great information! Thank you for taking the time to share your knowledge with us. It may save many lives in the future.

  3. Student

    I found this helpful, but was not alot of information on this topic if you where to make a paper on telling how to purify water, and how to gather it.

  4. anjuman

    there is always a difference in comprehension through reading and learning it through videos. putting demo videos would be a good idea. thank you for all the useful info.

  5. ahmed ali ahmed

    thank you for the right answers that i really need it. thank you very much

  6. heidi mackey

    Thank you, Todd for the update on not using iodine for water purification. My husband is allergic to shellfish.!!

  7. PurePlanetEssentials

    This a great article with some very useful and important information for survival depending on what type of situation you’re in. One of the most important aspects of water purification that is overlooked is the pH level of water. A pH level of 7 is the optimal level for water. When water has a pH balance of 7, water reaches an alkaline state. Drinking alkaline water regularly, helps your body to hydrate itself as well as flush out toxins and waste products. If you’re trying to lose weight, you may get a boost there as well. Overall, there’s no better way to help stay healthy.

  8. Logan Thybolt

    Good article but i am doing a project on ” How would you survive on a deserted island with only the clothing on your back (you have to find resources such as water, clothing, food, and shelter)?” and i cant figure out how to purify salt water with only natural resources. Please help.

  9. Bob

    It’s true that many people recommend boiling water for 2 – 3 minutes, or longer, to be safe. However, according to the Wilderness Medical Society the reality is that when the temp of the water rises above 160° F (70° C) it will kill all pathogens within 30 minutes. When the temp rises above 185° F (85° C) it kills them within a few minutes. So by the time water reaches its boiling point of 212° F (100° C) all pathogens will have been killed. But for most of us what’s another minute or two for peace of mind? Loved this article… great information and a bookmarked resource!

  10. Hach

    Hi its is a really good aritcle, but I am curious on one How do you on a large scale purify salt water for more than a 100 people living in a remote area. Lets say the situation is that they dont have alot of resources to deal wit no ground water, they live on a island, not a lot of firewood and there has been a drought for over 6 months.

    Could you all please submit your solutions to this challenge.

    • Vermster1up in reply to Hach

      Have you tried collecting water from trees through the transpiring of there leaves? Basically placing a plastic bag over a tree limb with its leaves.

  11. pazke

    According to the CDC, water need only be boiled for 1 minute to make it safe for drinking. Since fuel may be scarce, a shorter boil time would be beneficial.

  12. Marvin

    Was wondering in a land like the Sahra desert and sea water was pumped about 400 miles into the desert how fare from there would the water be free of salt as the sand filterd the water.?

  13. Vermster1up

    Thomas J. Elpel mentions in his book “Botany in a day” that he will ingest some mint plant with any water that might be questionable in an emergency situation. I have been trying to elaborate on this technique, there are many plants that show antibacterial,antimicrobial, and are also effect against protozoa mint being one. So it could be possible in an emergency situation to use something like crushed up peppermint plant to disinfect water. Still researching it but looks to be interesting.

  14. I find it interesting that the CDC recommends 8 drops of the correct bleach per gallon of water while the FEMA/Red Cross pamphlet recommends 16 drops per gallon. That is a wide gulf. I wonder who is more correct? I really like these new filtration “straws” that are out now and the canteen by I think Ndur or something like that can filter 100 gallons of questionable water with one filter. Those kinds of items seem like a great way to insure you have a continual supply of water. Good article by the way. My favorite tidbits were making your own water distillation system, that is a new one for me.

  15. Rhonda Givens

    I recently went camping and was confronted with water that had a natural tanning to it. The water was a deep brown/red color and a rotten smell! I used the charcoal and gravel technique and was simply amazed how the water tasted and smelled. The fish seemed to thrive in this deep murky red water, but I was doubtful. By the way I was in Florida, I was very worried about bacteria.

  16. Jim Scott

    There are two different concerns with drinking water. The first are disease causing pathogens, agents include bacteria, viruses, protozoa, and parasites. The second are with particulates and chemicals dissolved into the water which boiling alone does not eliminate.

    With the first concerns, the scientific evidence is that disease-causing organisms are dead long before the water reaches a boil. So there is no need to boil pass the point where is starts to boil. The act of heating until one sees a boil assures that more than an adequate time & temp. has been achieved without the need of a time piece or thermometer. The temperature and time required is inversely proportionate. That being, the lower the temp. the longer time required and the higher the temp. the less time required. Pasteurization a process applied to many food and drink products, to render them safe is carried out at temp’s between 60 to 70 c (140 f to 168 f). Be assured, heating to a boil is a simple process that inactivates all problematic pathogens. If fuel is a concern after a boil allowing the water to cool covered renders further reassurance, while not required. Is the water sterilized? No. Some bacterial spores are heat resistant, some survive for long periods in boiling water (100 c or 212 f) . They are everywhere in the natural environment but they are not waterborne pathogens to be avoided or should not raise any health concerns, that I know of or understand it.

    With the second concerns, chemical and dissolved solids (like salt, arsenic, etc.) can be removed via or vapor (solar) or steam (fire) distillation. While traveling to third world countries or out in the wilderness any where bring water orproceed accordingly (above). :)

  17. There are lots of methods by which you can treat the waste water. The technique to be utilised depends on the quantity you want to manage as well as the level of contaminants you are coping with. Thanks!


    Mr. Scott is right. If it’s not dead by the time the water boils it’s not going to die necessarily by boiling it for five minutes longer. You’re just wasting valuable time and fuel.

  19. talia kane

    where the heck are you going to finde iodine or aq filter in the wild!!!!!!!!!!!!!!!!!!!!!!!!1

  20. Billybobjoebob

    Has anyone thought of boiling maet before eating if you cant get anything to hold the meat up? I am doing a research report for a class i ould like to know. If you can find out thank you.Thanks for reading.


  21. Billybobjoebob

    Hey I have another question. I would like to know if you can use other fiters becuase i live off of survival shows, but they dont explain how to set them up?!

  22. martin smith

    ive just move into a barn conversion and theres natural springs everywhere and that got me thinking about saving this water in bottles for the summer.
    I think ill boil it and so what its a bit flat but if its ice cold or could make ice cubes from these natrual springs i think it will say me a lot of money

  23. ramjbose

    i want to purify a soup water …., is it possible ..,

  24. RoseRaw

    Many plants will also help with the purification of water. However, if you are not familiar with mountainside plants, do NOT attempt! !
    Boiling seems to work 99% of the time.

  25. Eric Riddick

    Good article about how to make potable water in the backcountry!

    As an Eagle Scout, former Philmont staffer and long time backpacker, I agree with the author’s ideas regarding how to purify water properly. Taking shortcuts on this issue leads to illness and people dont believe it will happen to them, until it does. I have known personally several backpackers who “got lazy” and drank untreated water from crystal clear, bubbling streams in the mountains, yet still ended up with a nasty case of Giardia. It can take months to fully recover from Giardia. The shortest amount of time Ive heard is about a month recovery.

    I consider this issue of making sure you purify your water a form of personal discipline, while backpacking or practicing wilderness survival skills or primitive camping.

  26. lloyd howell

    hi iwould boil water at least 10 minutes that way your sure i was a navy seal dont use iodine if you have a seafood allergy

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