Disinfecting Water in the Field


One of the top survival priorities we have is always going to be hydration. Studies show that upwards of 75% of adults in the USA suffer from chronic dehydration due to not consuming enough water daily. People regularly drink sodas, coffee, juices and other beverages that quench their thirst but these beverages actually speed up the dehydration process rather than actually hydrating the body.

There are many different recommendations out there for the minimum water  consumption that your body actually needs to stay properly hydrated on a daily basis. I believe the number may actually vary slightly from person to person based on weight but a general number that seems to be repeated by many is 64 ounces or a half gallon. Keep in mind that if you are exerting yourself, which we often do when we are afield, you will need more and possibly much more. This is especially true if you are operating in arid or hot climates. As our body sweats and looses water through perspiration, we have to replace those fluids for our body systems to continue to function properly.

These facts reinforce for us as woodsmen just how important the ability to disinfect water while in the field actually is. It is without a doubt one of the most important skills we can possess for survival in the short-term and especially for the long-term.  Let’s discuss some of the most effective and proven methods to disinfect water in the field.


Boiling water is absolutely one of the most “sure fire” ways to ensure that any biological contaminents that may be lurking in your water are dead. By biological, I am referring to  living organisms such as bacteria, viruses, protozoa, etc. If proper precautions are not taken to disinfect your water, these organisms can get into your digestive tract and reek havoc on your system. Bringing water to a boil ensures that you are killing these possible pathogens and making your water safe to consume assuming that there are no harmful chemicals, fertilizer, heavy metals, etc present in the water. Keep in mind that water boils at 212 degrees Fahrenheit at sea level. With each 500 feet of increase above sea level, the boiling point lowers by 1 degree. Therefor, at higher altitudes it is a good practice to allow the water to boil for 2 to 3 minutes to make sure it has hit the critical 212 degree temperature mark.


There are many commercial filters on the market and I have used several of these with good results. Some filters are straw type filters that allow you to drink directly from the source and others are pump type filters which allow you to draw water from the source and push it through the filter and into a container for consumption or storage. One filter that I have always had good results with is the Sawyer Mini. It has several options for how to use the filter and is quite versatile. It is also among the most affordable of the commercial filters on the market and can be easily found online or even in local big box stores. Other filters I have used include the Katadyn Hiker Pro and the Life Straw. I have never been sick drinking water from ground sources using either of these filters. Always carefully follow the instructions from the manufacturer of the filter and keep in mind that most are disposable after a certain amount of usage.

Improvised Filters:

There are many ideas out there on how to improvise a water filter but none of them are truly safe. Not to say that they couldn’t work, but the versions of improvised filters I have seen and experimented with are only last resort measures and would only be recommended by following up with boiling the water that has been filtered. Improvised filters involve pouring water through a medium of small pebbles, sand and pulverized charcoal. These filters can be effective at removing sediment from water collected from questionable sources and they do serve to make the water more palatable in taste and appearance. I have personally experimented with the tripod method with 3 bandanas hung, one over the other and each containing a finer medium from top to bottom. While the water that came out from the filter appeared to be cleaner and contained very little to no sediment, I still boiled it before consumption just to be safe.

Tincture of Iodine:

Ticture of iodine can be added to questionable water to disinfect it if used in the correct proportions. The general thought is to use 5 drops per quart if the water is clear and 10 drops per quart if the water is cloudy. You should always strain the water through a clean cloth such as a bandana or t-shirt before treating it with iodine. This helps to remove any sediment that may be floating in the water. After you add the iodine, you should wait a minimum of 30 minutes to allow the chemical to work. In colder temperatures it may take longer for this process to work. If the water temperature is 40 degrees or less, allow double the time for the chemical to take effect. Once your water is treated, you can pour it back and forth between containers to improve the taste or you can add something to flavor the water such as salt or even a drink mix. If you are in a woodland environment, pine needles can be used to flavor your water and will even add vitamin A and C to the water to give your immune system a boost. Allow the needles to steep after the water is boiled for 5 to 10 minutes to allow these nutrients to leach into the water making a tea. Another benefit to carrying tincture of iodine is that it doubles as an antiseptic for wounds should you have the misfortune to take an injury while out in the field.


Bleach is another chemical that can be very effective at disinfecting water. As with Iodine, it is a matter of using the right proportions. A general formula is to use 2 drops per quart of water or 8 drops per gallon of 6% Hypochlorite Bleach. If using 8.25% Hypochlorite Bleach use 6 drops per gallon or equivalent. It is important to make sure that the bleach you use is not scented or doesn’t have any other cleaning agents in it for laundry use. After you treat the water, allow it to sit for a minimum of 30 minutes. If after this time the water smells strong of bleach, pour it back and forth a few times between 2 clean containers and let it sit for a few hours. Remember as before, you can use flavorings to make the treated water more palatable.

These are the methods of emergency water disinfection that I have become familiar with over the years. In the field, 99% of the time for me personally, I filter my water through a bandana to remove sediment and then boil it well. Again, I have never been sick when consuming water from the landscape using these methods. On multiple occasions I have even consumed water raw and still never had any issues but I will never recommend to do this unless there is no other option. There may be other options for achieving water disinfection in the field but these above methods are the total of my personal experience and so I wouldn’t feel qualified to speak on other methods.

The final thought here is that throughout this article, I have very purposefully used the word “disinfect” as opposed to “purify”  as none of these methods are 100% guaranteed to purify water. They do however give you the best and most effective methods that I know of to help you consume water off the landscape as safely as possible.

Matt Mercer


2 thoughts on “Disinfecting Water in the Field

  1. Informative and to the point.
    When collecting water from a source try to collect moving water. Even if it is just barely trickling, i was taught moving water is better than standing water.


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