#AskPaulKirtley Episode 39 – Wilderness Water Sources & Water Purification

by Paul Kirtley

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In this episode of #AskPaulKirtley I answer a bunch of questions about water. What are the advantages of Millbank bags? Can you use a bandanna to filter water? Do Steripens work? How do you deal with herbicides and pesticides in water? Can you use activated charcoal to filter water? Is it safe to drink water from springs and wells? These are the jumping off points for a wide-ranging discussion about producing safe drinking water outdoors – close to home or further into the wilds…

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Links For This Episode of #AskPaulKirtley

Water Purification: The 5 Contaminants You Need to Know About

How to Use a Millbank Bag: 6 Easy Steps

Does Boiling Always Make Water Safe To Drink?

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What Is #AskPaulKirtley?

#AskPaulKirtley is my Q&A video and podcast series that aims to answer your questions about bushcraft, survival skills and outdoor life.

The idea here is partly to take the strain off my email inbox and get answers out to people in a more timely fashion.

Rather than send an answer to just that one person, I’d like others to benefit from the answers too. So, just in the same way I’d previously write an email answer, here I’m going to speak the answer (which is much quicker than me typing out an answer, so I’ll get more questions answered as well as benefiting more people).

Click here to find out the different ways you can ask me a question.

Related Material On Paul Kirtley’s Blog:

#AskPaulKirtley Episode 18: Power In The Wild, Water Purification, Chaga & What I Have In My Pockets

#AskPaulKirtley Episode 4 – Biting Insects, Wild Foods, Tree ID and Water Purification

How To Generate Water In The Frozen North

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Paul Kirtley is an award-winning professional bushcraft instructor. He is passionate about nature and wilderness travel. In addition to writing this blog Paul owns and runs Frontier Bushcraft, a wilderness bushcraft school, offering bushcraft courses and wilderness expeditions.


{ 4 comments… read them below or add one }


No matter how many times he said “protozoa cryptosporidium” Harry Potter’s water purification spell wasn’t going to plan. So he turned his wand into a featherstick, set fire to it and boiled the water instead.


Pär Leijonhuvud

Improvised water filters (charcoal, sphagnum moss, etc).

The Swedish army developed a version of these, and found that while they worked at least to some extent to remove radioactive and chemical pollutants they tended to actually add microorganisms to the water. After several incidents when people got sick they banned it (in the army you can give orders… :-). So while your advice was acceptable for the question (chemical contaminants), it really ought to have the caveat that you *must* boil the water after the filtration step before you drink it.

P.S. If you want to I can check if any of the studies were non-classified and send them to you.


Pär Leijonhufvud

And good answer to the “can I use charcoal for water filtration” question. In the lab I could probably (I have never tried it, so I don’t know for certain) produce an activated charcoal column that would filter water sufficiently to make it safe to drink, but that would be a carefully packed liquid chromatography column prepared over many hours (letting a fine slurry of very even charcoal particles pack down under constant gentle water flow for several hours, etc). Not a trivial thing to improvise in the field! Besides, for any reasonable sized column we are talking fairly low flow rates (say a liter/h)


Michael Sander

As always Paul, thank you very much for the great work you are constantly doing.

For the time beeing I used millbank bags (at your courses) or the very similar brown bags
(on my private wanderings) for course filtration followed by boiling. I found this to be
a very reliable and safe way to treat water found in nature and had never any problems, upset stomache, etc.

For some reason (don’t know exactly why) I am a bit afraid to use chemicals for water treatment
and so far I had not yet the opportunity to try one of the industrial made filters like Katadyn,
MSR or Sawyer.

I am also very skeptical regarding improvised water filters. I once have been teached on a
bushcraft course in Germany how to make one: the bottom of an empty PET bottle was cut off and
the bottle was then filled with tightly packed layers of charcoal, sand and grass. The bottle
was hung up upside down and was filled with murky water. A small hole was poked into the lid
of the bottle to give the illusion of a very low flowing rate. When the lid was removed, however,
the water flew almost unimpeded through the system which convinced me that there was not much
filtering going on. The murky water was slightly lighter in colour but I didn’t want to drink
it without boiling as suggested by the instructor.

Later on I found this article on an experimental series of the renowned Norwegian School of Winter
Warfare ( http://survivology101.blogspot.co.at/2015/03/water-water-everywhere-but-not-drop-to.html?m=1 ) and learned that plant material and sand have almost no filtering effect regarding bacteria whereas charcoal seems to work to some extend.

However, as you already said in the video, it’s not a reliable way to remove pathogens from water as it
works just by chance and should at least be supplemented by boiling.

Kind regards from Austria


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