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#291690 - 01/25/19 07:30 PM Boiling Water - How long?
hikermor Offline
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Registered: 08/26/06
Posts: 6817
Loc: southern Cal
There is fairly universal agreement that boiling water is the best way to rid it of pathogens, but the recommended boiling times vary widely:

"Simply bring the water to a rolling boil and maintain the boil for one minute, regardless of elevation." [/i]Mountaineering; The Freedom of the Hills[i] 8th edition, p. 65

"for safety, you should always boil water furiously for at least five minutes. Increase the boiling time at higher altitudes..."[/i]Outdoor Survival handbook[i] Raymond Mears, p 55

My favorite: "CDC and the EPA recommend boiling water for a full minute (three minutes above 6500 feet... because water boils at a lower temperature.... [/b]However simply bringing water to a boil is just as effective[b]" (emphasis added). [/i]Medicine for Mountaineering[i] James Wilkerson, 6th edition.

I read recently on one internet source, which for various reasons I did not consider reliable, that one should boil water for five minutes, increasing by one minute for each 1,000 foot increase in elevation. That would mean fifteen minutes of boiling at 10,000 feet. If there is any water left in your pot it certainly should be sterile....

Wilkerson makes the point that milk is pasteurized by bringing it to 160F for 15 to 20 minutes. Just in case you were wondering, water boils at 165 degrees on the summit of Everest, so boiling works just about everywhere....

These days I bring water to a boil and then make either coffee, tea, or oatmeal (maybe FD meals), but I wonder if anyone knows of any definitive studies or experiences with boiling water.

I have, in the past, often imbibed from mountain sources without any treatment whatsoever, but mostly that was some time ago, when trails were less traveled. I generally treat water one way or another these days.


Edited by hikermor (01/25/19 07:52 PM)
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#291691 - 01/25/19 07:55 PM Re: Boiling Water - How long? [Re: hikermor]
Ren Offline
Member

Registered: 11/05/07
Posts: 144
This is a general "Water treatment for International Travellers" article. Though it does detail temperature/time of various bacteria and viruses, and has references to sources.


https://academic.oup.com/cid/article/34/3/355/388050#

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#291692 - 01/25/19 07:58 PM Re: Boiling Water - How long? [Re: hikermor]
Russ Offline
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Registered: 06/02/06
Posts: 5074
Loc: SOCAL
Hmmm, I carry one of those pocket thermometer thingies (to use a technical term) that is used so I don’t have to guess how hot or cold water happens to be. Does anyone know the temps required to kill the various bacteria, virus’s or other pathogens? If you know the temperature that kills them, you don’t have to be concerned about elevation lowering the boiling temp of water, or extending the time so long there’s no water left in the container.

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#291693 - 01/25/19 09:55 PM Re: Boiling Water - How long? [Re: Russ]
dougwalkabout Offline
Crazy Canuck
Carpal Tunnel

Registered: 02/03/07
Posts: 2742
Loc: Alberta, Canada
Actually, Ren's link has charts with temperature and duration. I can't claim to be an expert, but this looks like credible info to me.

Personally, any "extra" boiling after the 1-minute mark depends on the water source.

For a glacier-fed mountain creek, achieving a full rolling boil is plenty -- I don't waste fuel.

On the other hand, if the source is the Amazon or equivalent, I'll boil the devil out of it if I can spare the fuel. I seem to recall that there are lots of spore-stage nasties in tropical water that are tough to kill.

Same goes for a water source with cattle in the area. Cattle are notorious for walking knee-deep into a water source, drinking on one end and simultaneously dropping cow-patties from the other -- ground zero for a huge e-coli load. Boil, baby, boil -- with some campfire charcoal if possible.


Edited by dougwalkabout (01/25/19 09:59 PM)

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#291694 - 01/25/19 10:18 PM Re: Boiling Water - How long? [Re: hikermor]
clearwater Offline
Old Hand

Registered: 03/19/05
Posts: 1093
Loc: Channeled Scablands
On a trip in Western China the locals cooked every food and drank tea made with water just brought to a boil. Much of the water came from cisterns that had livestock wandering about over the ground surface so sheep, pig and yak dung was everywhere. They reported that no one got sick from it. I didn't either. In fact I had trouble in the city from bottled water before I got to the highlands.

If the water is clear, I just bring it to a boil. Otherwise I filter or floc, then boil or treat with chemicals.

Washing hands is more important in my estimation.

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#291699 - 01/25/19 11:45 PM Re: Boiling Water - How long? [Re: dougwalkabout]
Russ Offline
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Registered: 06/02/06
Posts: 5074
Loc: SOCAL
Thanks, Ren’s post beat mine by 3 minutes, I was probably typing as he was posting. Good info at his link’s article.

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#291700 - 01/25/19 11:45 PM Re: Boiling Water - How long? [Re: clearwater]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 6817
Loc: southern Cal
Some years ago, I was in China on a caving expedition. I was the archaeologist and the EMT for the group. Naturally I expected a lot of cases of "Mao's Revenge". There were twelve of us, in country for a month, eating and drinking the local fare.

Not so much as an upset stomach. I am not sure what we consumed, because the wiser course was to just shut up and chew. I was told that our water was boiled regularly....
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#291701 - 01/26/19 12:54 AM Re: Boiling Water - How long? [Re: Ren]
hikermor Offline
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 6817
Loc: southern Cal
from the article posted by Ren:

"Because the time required to heat water from a temperature of 55°C to a boil works toward disinfection, any water that is brought to a boil should be adequately disinfected. Boiling water for 1 min or keeping water covered and then allowing it to cool slowly after boiling can add an extra margin of safety [37]. The boiling point decreases with increasing altitude, but this is not significant when compared with the time required to achieve thermal death at these temperatures."

Short boiling times, especially when slow cooling is employed, would seem to be adequate.

Thanks a bunch for this very thorough discussion!
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#291703 - 01/26/19 05:34 AM Re: Boiling Water - How long? [Re: hikermor]
Phaedrus Offline
Pooh-Bah

Registered: 04/28/10
Posts: 2245
Loc: Great Plains
Personally once it's at a boil I'm done. It doesn't need to boil for more than a few seconds. One minute at a boil is overkill.
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#291706 - 01/26/19 05:25 PM Re: Boiling Water - How long? [Re: hikermor]
Montanero Offline
Veteran

Registered: 10/14/08
Posts: 1473
Loc: North Carolina
I have seen all of those methods taught. From my understanding of biology, bringing water to a boil is sufficient for most killing most pathogens. The process of heating it up to boiling, and then cooling it down, exposes the biological pathogen to high enough temperatures for long enough. If you want to be sure, do it longer, if you have the fuel. If you strain all of the suspended solids out, it will improve the effectiveness (of all purification methods).

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