Hiking : Water sources & water purification


We tend to carry all of our water now plus extra (actually, read that as I tend to carry the water, my girlfriend carries the food - not sure about the arrangement there…).

We tried using the chlorine type tablets in Morocco 2014 when climbing Toubkal and we had no choice but to use stream/lake water. I ended up being a bit ill, which my GP thought may have been Giardiasis:
Giardiasis - NHS

Having recently spent a couple of weeks climbing some >2500m mountains in the Swiss Alps, I know what you mean about using up the water quite quickly. Luckily a lot of huts do sell water, which you can plan for using hiking maps and a bit of Googling to check they are open (you may also need a lot of cash - my worse bill was when I spent almost £50 on 5x bottles of 1l water on a long distance overnight trip)!

We also take a small gas stove and 100g gas canister, just in case we need to boil some locally sourced water. You can’t beat a hot cup of tea on a summit as well! :slight_smile:


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For years I have used bleach for water, then a Pur Hiker filter system, then carried enough for the trip, now back to a purifier system that light, easy for field maintenance and doesn’t kill the bank account. It is a Sawyer SP128 Mini Water Filtration System. Fast, no not really compared to a filter with a pump but it works great for me.


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When I thru-hiked the Appalachian Trail I used Aqua Mira drops (chlorine dioxide, I believe). They are very lightweight, but you have to wait 30 minutes for the chemicals to work. They also don’t leave any taste, which is a big plus for me.
Since then I’ve purchased a Sawyer Mini filter. I’ll take one option or the other depending on how long I’m going, and how many people I need to treat water for.

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I drank Afghan mountain water treated with iodine tabs, didn’t die.

-Doug, ND9Q

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“I ended up being a bit ill, which my GP thought may have been Giardiasis” :fearful:

I used Hydroclonazone in the past because it did not give a bad taste to the water as well.
But then I realized recent tests found it to be insufficient to treat water.
If Aqua Mira works and it has no bad taste then it is a big thumbs-up.

Iodine works but using it too much may be a concern.
I am guessing this was (is?) standard Army issue.
Is that what the US army currently recommends for soldiers in the field?

The Marine Corps has been using an MSR MIOX Purifier for the past couple of years. MSR has a commercial version (it’s red in color vs coyote brown) that’s sold to the public. It’ll treat viruses and bacteria. Uses salt, water, and batteries. While visiting my son down at Camp Pendleton a couple months back, he showed me the newest one coming down the pike. It’s currently in field testing, and had to be turned back in once he transferred. I would have liked to have that one find it’s way into my pack on the way home! :wink: Here’s some info:

We both have the Sawyer Mini’s too.

73, Todd KH2TJ

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Interesting info, thanks Todd. I had never heard of that, mixed oxydants using salt
I am sure the marines have done their homework so it is good to know what they’re using.
It seems there’s a wait time though which does not sound so convenient for a Marine on the go.
Users seem pleased with the civilian version of it.

Yes looks like the Sawyer Mini is coming to my backpack this summer.


I’ve produced drinkable water from some really ugly sources…ponds, etc. What I have learned is the following process:

  1. Use paper coffee filters to screen out the big “stuff”. This will leave you turbid, maybe algae-green water.
  2. Filter that with a good ceramic filter like the Sawyer or MSR filters. That will get you drinkable water but you will have to clean your ceramic filters more often.
  3. Then use AquaMira drops for the final step to get cryptosporidium or other viruses. Virus contaminated water is rare in mountain streams; not so rare around city streams that can get raw sewage runoffs.

Be aware that when at altitude, water boiling temps are much lower. A general rule is 2-deg F for every 1000 ft of elevation. Just means you have to boil water longer…


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Great discussion, and timely as I am considering longer hikes. For day hikes I always tank up as I drive or at trailhead on a liter or 2 of Green Smoothy (Greens and Fruit) chock full of 15-30 ml Chia seeds. I can forget about water for an hour or so and sometimes reach the summit without touching a drop.

Tank up is a good idea. For longer day hikes or overnight best to start well hydrated, more important if there is an alternative water source to the one in your pack at the start of the hike. May sound a bit obvious but I need to remind myself to do it.
Slightly off topic, My Camelbak 3 litre short Milspec bladder arrived today. This is to replace the Osprey one. Feels a much better quality and more compact. Have some comments on my sota gear blog.

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Good tips, thanks!
I typically have access to clear water but filter + aquamira sounds like a good combo.

Regarding tanking-up, I have read that you should do it in the evening before the hike as you body cells become more hydrated and thirst will come later. If you combine that with a pre-hike top-up then you should be “golden” for a while. You may have to plan for more time though if you have to stop every 10 minutes… :grinning:

Even better, use a 0.5 micron filter to get rid of cryptosporidium cysts and other big stuff.

Chlorine dioxide kills viruses and bacteria quickly, but the crypto cysts are very tough. They can survive in undiluted bleach for 24 hours.

In clear 20ºC water, chlorine dioxide kills everything, including the cysts in 15 minutes. In cloudy, cold water, it can take four hours. The cysts can be as small as 4 microns, so the 0.5 micron (absolute) filter takes care of them.

I use a $3 filter from Duda Diesel, designed for filtering biodiesel fuel.


I learned about this filter from Roleigh Martin, a very active hiker on the John Muir Trail.


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The US Centers for Disease Control (CDC) has an excellent summary of the various water purification methods.

Chlorine dioxide is the active ingredient in Aqua Mira, Katadyn Micropur tablets, and the MIOX device. Cities generally use chlorine dioxide or chloramine for water treatment.

Philmont Scout Ranch gives out the Micropur tablets for Scouts on treks there. They have 25,000 participants each summer, going on eleven day treks, so that is a quarter-million trail days. There is livestock throughout the ranch. If it works for Philmont, that is a pretty good recommendation.

Aqua Mira is fussier than the Micropur tablets, but much cheaper. I use it and I teach the older Scouts how to use it. The tablets are pretty foolproof for the younger Scouts.


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And I learned about it from you.
Went to their web site, and some are on the way. Thanks!

There was a time…long ago, that all you needed for water in the Sierras was your Sierra cup…sigh.


I did that in the Pecos Wilderness back in the 1970’s. I remember a lovely trailside spring with a tiny waterfall just tall enough for the cup.


Hi everybody

just an idea - https://www.steripen.com/

My daughter used it last year for her 4 week trip through Nepal. She came back healthy and had no problems during her trip.

I think it is based on this Solar water disinfection - Wikipedia and helps in many situations.


I dont have the data right at hand but the topic of viral contamination and its treatment comes up from time to time in the hiking communities. Everything I have ever heard is that if you are out in the wilderness or countryside (where SOTA activations typically occur) of a developed country that has basic sewage treatment and garbage handling, then the odds of viral contamination of surface water is extremely low. I know here in the US it is extremely rare.

Thankfully I have only had to use sterilisation on one extended day out on the hills in Scotland. The stream was fast flowing and clear, but I still used the chlorine dioxide tablets in my pack having remembered drinking directly from a clear running stream in my youth, later finding a dead sheep lying in the water about 200 metres upstream.

The tablets have now gone out of date, so need replacement. I don’t think I will be buying the same again as the water tastes absolutely foul with this treatment!


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