So, riddle me this expert lightweight packers. What temperature does water really need to reach in order to be safe to drink? Full boiling? Full boiling for five minutes? Close to boiling? Visible bubbles? Seems like there is a fair amount of discussion on this topic, I'm interested in hearing some of your perspectives. Thanks!

In the US all you need is a full boil in most cases. If at high altitude water boils at lower temps so can need longer boiling. Even then, we don't have the issues that some other countries have with disease in water.

Good clarifying point. This is for USA, Sierra Nevada 8,000-11,000 feet. Thanks.

I posted this a couple seconds ago on the FBC thread - this should help also here :-) This pertains to when water boils.

Sea Level
212*

2,000 ft
208*

5,000 ft
203*

7,500 ft
198*

10,000 ft
192*

So, since boiling point is variable then what is the temperature and duration to kill the nasties? I'll add that this is for about 1 liter of water used for cooking only so I have no need to get the water to boiling for the food, only to sterilize. We use iodine for drinking water.

The suggestions I have seen is that at high altitude to let it boil till it reaches that temp. One way to learn how long is to take an espresso thermometer (the type used in steaming milk, costs a couple bucks) with you on a trip. Plop it in the water when cold, then leave it till it boils. Start timing and watching, when it hits 212* you know how long for the rest of time.

In all honesty though? I bring my water to a roaring boil, then turn off. I don't waste fuel on extended boils.

Thanks. We are pushing an alcohal stoves limits here. 2 parents, 2 kids, would ideally like to boil 6 cups of water so I have enough in one boil for 2 dinner entree's and hot cocoa afterwards all kept toasty in my Nalgene Cozy. It has to be more fuel efficient to do this all at once rather than two burns (not to mention I just don't want to bother with 2 burns).

I have the TiTri Caldera and with max fuel of 45ml, that's pushing the upper limits for hitting full boil of water with my Evernew 1.3 liter pot full up, hence the questions.

Here's a secret-

Water in common backpacking areas of the Sierra Nevada is very unlikely to have Giardia, viruses, or protazoans in it! It is likely to have coliform bacteria if you're downstream from areas used by grazing or pack stock.

Bacteria is all dead within a few seconds after your water passes 160F. 175F for a minute is enough to destroy Giardia cysts.

My sources are articles by Dr. Robert Derlet in the Wilderness Medical Society Journal (WEMjournal.org) and those posted by Dr. Robert Rockwell about Giardia at various web locations.

Edited by jimqpublic on 11/23/2009 17:28:38 MST.

I lifted the following quote from the CDC website advice on treating drinking water:

"Boil filtered and settled water vigorously for one minute (at altitudes above one mile, boil for three minutes)."

CDC seems to think that you're dealing with highly contaminated water and instantly going from room temp to boiling, then from boiling back to room temp.

In reality the water spends a few minutes heating up, then more time cooling back down. Also at higher altitudes (in USA & Canada) the chances of upstream pollution tend to drop, so the lower boiling point is somewhat offset by lower risk of contamination.

I believe bringing the water to a boil, then cutting the heat off is more than sufficient for the Sierra wilderness areas.

" believe bringing the water to a boil, then cutting the heat off is more than sufficient for the Sierra wilderness areas."

+1 Pasturization takes place at ~155 degrees. If you have a thermometer, bring the water to perhaps 170 and call it a day. The dwell time above 155 should be at least a minute, adequate to kill coliform bacteria and viruses.

"+1 Pasturization takes place at ~155 degrees. If you have a thermometer, bring the water to perhaps 170 and call it a day. The dwell time above 155 should be at least a minute, adequate to kill coliform bacteria and viruses."

Thats the answer I want to be true! Thanks! Huge difference in burn time to reach 170 vs full vigorous boil.

These numbers (170F) sound close to what I remember while serving in the US Navy. The water for crew & boat was made by use of an Evaporator. It boiled sea water at a lower than normal pressure and temperature to maximize efficiency— thus less Uranium was needed :). The “magic number” I remember was that the water had to have a minimum temperature of 166F—to kill all of the bacteria in the sea water.

I'd agree on the CDC alarmist comments - you gotta remember that those guidelines are for floods, natural disasters and when sewage breaks loose. Then you do wanna boil the heck out of your water.

The only places I ever worry about is when there is livestock in the area - usually cattle and or when I am camping near runoff from agriculture. And then I just pack all my water in.

"CDC seems to think that you're dealing with highly contaminated water and instantly going from room temp to boiling, then from boiling back to room temp.

I'm not sure it's possible to know what the people at the CDC were thinking, but I doubt that they were assuming some sort of flash boil capability. It's possible that they're being conservative -- their goal is to see to it that no one gets sick after all -- but if they are being overly conservative, I would be more likely to be convinced of that by a rebuttal that comes with credentials.

Anecdotal evidence is mostly meaningless. I've had people tell me they've never worn a seat belt, never had even a close call talking on a cell phone while driving and a host of other nevers. It could well be that they never will suffer any adverse consequences, but there's a body of statistical evidence that they have elevated the likelihood that they will.

A vigorous or rolling boil is recommended as it is an easy visual cue that the water is above the temperatures needed to render the water safe to drink, without using a thermometer.

My understanding is that 180 degrees F is the temperature needed to destroy pathogens.

Minor clarification:

I believe another post implied you could increase the temperature of boiling water by boiling it longer. This is not the case. The altitude (air pressure) determines the boiling temperature.

Once boiling, water will not get hotter, no matter how much heat is added. Adding more heat just makes it boil faster. This is the nature of first-order phase transitions, where e.g. water (liquid) is converted to steam (gas). Such transitions involve the "latent heat of evaporation" of the material, water in this case.

This means that heat is needed to convert liquid to gas at a constant temperature, and all heat added goes into converting more liquid to gas, and does not increase the temperature.

Once all the liquid is converted to gas, then the temperature of the steam can be increased by adding more heat. This is done e.g. in closed steam heating systems, power plants, etc.

Good information on boiling times here

http://www.survivaltopics.com/survival/how-long-must-water-be-boiled-revisited/

The temp required to kill PATHOGENIC bacteria is around 160. that's why they recommend meat be cooked to 160 (remember this on Thanksgiving folks). liquids should be held there at least a minute, probably more just to ensure that the whole volume has been evenly heated. Stirring with the thermometer is a good idea. There are some bacteria that can survive higher temps, but they live in geysers and hot springs and are not going to make you sick even if they do somehow find their way into your water.

when they pasteurize beverages, they don't boil it, they just bring the liquid to just high enough to kill the vast majority of bacteria (but not all, which is why milk will still eventually go bad). But they have all kinds of fancy instruments to measure temp through the process. "ultra-pasteurized" liquids have been more intensely heated for a longer period of time, and are totally sterile. these can be left unrefrigerated until opened.

The reason they usually say "just boil it" is because that provides a guaranteed, idiot proof way of knowing the whole volume of water has reached at least 160, regardless of altitude. Because really, How many people actually carry a cooking thermometer with them?

Edited by hobbitling on 11/24/2009 11:05:12 MST.

When getting all my shots for traveling abroad, my doctor told me that 99% of water will be okay if when heated, you could see the tiny bubbles at the bottom start to dance a bit.

I also remember an article in the LA Times several years back about the Sierra water quality. Apparently, the top 2-3 inches of lake water are so bombarded by UV, that it is very safe to drink.

I am still of the mindset that Aqua Mira is so easy, it's not worth getting crypto or giardia.