boil water for 5 minutes, or 0 minutes?

[Ben Crowell]

I believe I recently read a book that stated that simply bringing water to a boil is enough to kill all microorganisms. (Possibly this was in Mountaineering: The Freedom of the Hills.) But yesterday I met a hiker who claimed it was safer to boil the water for 5 minutes. Anyone have any definitive info on this?

It seems unlikely to me that any health-threatening bug you'd realistically encounter could survive even being raised to close to boiling, so probably the only reasons you'd want to bring the water to a boil would be (a) you're about to use it in cooking something that requires a full boil, or (b) you don't want to have to carry a thermometer to tell when you've got the water to the necessary below-boiling temperature.

[Bob Gross]

The answer depends on what kinds of microorganisms you want to kill. (There is stuff growing in the virtually-boiling geysers at Yellowstone.)

When I am high in the mountains, about the only organism that I feel the need to kill is giardia lamblia. It has a kill temperature of 175 F. So, at any reasonable elevations, just bringing your water up to boiling at 190-210 will kill it.

Now, there could conceivably be some bacteria and virus problems, but not where I've been hiking. Nearly everything will be killed by the same boiling temperatures.

If you go up to 20,000 feet elevation, this rule of thumb no longer applies. As I recall, the 175 F boiling point is reached around 19,500 feet.

–B.G.–

[Brian Turner]

Everything I've read says you only need to bring the water to a boil but not necessary to continue boiling.

[Anonymous]

"But yesterday I met a hiker who claimed it was safer to boil the water for 5 minutes"

I've heard numbers all over the map on this one. Bacteria and viruses will be killed by the time the temperature hits ~160 degrees. Giardia take longer to kill, especially in cyst form. That may be where the 5 minute figure comes from. However, heating water to a near boil uses a lot of fuel, and heating water to boiling uses even more due to the extra energy required for phase change from liquid to gas. It quickly adds up if done multiple times/day over an extended period. You'd be better off taking a Frontier Pro @ 2 oz and filtering out any lurking giardia before heating your water. That way, by the time the water reaches rehydrating/cooking temperature(bubbles on bottom of pan for many folks), any viruses/bacteria will have been killed and you will have saved a lot of fuel/reduced the amount of fuel you will have to carry.

[Marc Eldridge]

ran across this a while back

http://solarcooking.wikia.com/wiki/Water_Pasteurization_Indicator

[Sarah Kirkconnell]

The only times I would worry is in 3rd world countries. As long as the water boils you are safe in most cases….if I was traveling where bad nasties live, well….then yes, a longer boil might make you feel better – but what you want to kill here in the states is killed once it boils.

[Ben Crowell]

Thanks, all — very helpful!

The wikia link has some good numbers for various bugs, including viruses, and seems to make clear that long before you get to a boil, anything that is likely to be present and harmul will be dead. But their figures, which include viruses, make me wonder — I've seen a lot of discussion of what treatment methods will kill viruses, but I've never seen any statement of whether there are actually any specific known viruses in backcountry water that can make you sick. Does anyone know? The one the wikia article mentions is Hepatitis A, but I would guess this is more relevant to the third-world environments they're concerned with, not backcountry water in the US.

[Bob Gross]

I agree with Sarah. Hepatitis is the sort of water problem that you must expect in a Third World country. There are many tropical diseases and parasites that are waterborne. So, I get very serious about water treatment when I go to some places like that. OTOH, for the JMT, I would not worry so much, even if anything is theoretically possible.

–B.G.–

[Travis Leanna]

So we have boiling, tablets, drops, bleach, UV, filtering……what about low voltage electricity? This question may highlight my shallow understanding of bacteria/viruses/microorganisms, but that's ok. I'll even ask it again. Much like how Steripen "zaps" the water with UV, would a similar device work with sending a low voltage current through the water (or even a contained higher voltage)?

[Roger Caffin]

> would a similar device work with sending a low voltage current through the water

NO.

Cheers

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