Nov 23, 2009 at 3:43 pm #1242421
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!Nov 23, 2009 at 3:45 pm #1547496
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.Nov 23, 2009 at 3:47 pm #1547497
Good clarifying point. This is for USA, Sierra Nevada 8,000-11,000 feet. Thanks.Nov 23, 2009 at 3:49 pm #1547499
I posted this a couple seconds ago on the FBC thread – this should help also here :-) This pertains to when water boils.
192*Nov 23, 2009 at 3:57 pm #1547501
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.Nov 23, 2009 at 4:00 pm #1547502
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.Nov 23, 2009 at 4:12 pm #1547506
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.Nov 23, 2009 at 4:15 pm #1547507
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.Nov 23, 2009 at 4:20 pm #1547511
@herman666Locale: Northern Virginia
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)."Nov 23, 2009 at 4:28 pm #1547514
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.Nov 23, 2009 at 4:59 pm #1547517
Tom KirchnerBPL Member
@ouzelLocale: Pacific Northwest/Sierra
" 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.Nov 23, 2009 at 5:26 pm #1547528
"+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.Nov 23, 2009 at 8:11 pm #1547597
Steve MartellBPL Member
@steveLocale: Eastern Washington
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.Nov 23, 2009 at 8:45 pm #1547615
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.Nov 24, 2009 at 6:01 am #1547697
@herman666Locale: Northern Virginia
"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.Nov 24, 2009 at 6:36 am #1547702
@jdw01776Locale: Southeast Texas
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.Nov 24, 2009 at 9:11 am #1547740
Elliott WolinBPL Member
@ewolinLocale: Hampton Roads, Virginia
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.Nov 24, 2009 at 9:56 am #1547748
Good information on boiling times hereNov 24, 2009 at 10:02 am #1547749
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?Nov 24, 2009 at 10:10 am #1547753
Zack KarasBPL Member
@iwillchopyouhotmail-comLocale: Lake Tahoe
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.Nov 24, 2009 at 10:34 am #1547757
Hart –BPL Member
@backpackerchickLocale: Planet Earth
Cold is probably hot enough. If you are worried, boil it. Warm fuzzies.
Cryptosporidia and Giardia are present at least intermittently in much of US tap water. Generally not a problem for healthy people. May well be immune to it. Most of these infections are asymptomatic. If you're immunosupressed from AIDS or medications, need to be cautious.
Remember most campers get Giardia from their infected and more likely than not asymptomatic campmates. Not from the water.Nov 24, 2009 at 1:05 pm #1547802
"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."
I apologize for throwing out claims without backup. Anecdotal information leads me to believe that more backpackers get "stomach bugs" from poor bathroom sanitation habits of their companions than from water in the Sierra. Dr. Derlet's field research indicates that bacteria are the main waterborne risk in the Sierra.
Bacteria are quite heat sensitive and generally can be deactivated at fairly low temperatures. Giardia as well. Heating water to 160F for 10 minutes is more than sufficient to deactivate Giardia cysts.
"I am still of the mindset that Aqua Mira is so easy, it's not worth getting crypto or giardia."
Again, per Derlet's research Giardia is rare in the Sierra and Crypto is nonexistant. But if you are treating for their cysts the contact time using chemical treatment can be very long- up to 4 hours for complete deactivation. That can mean carrying a lot of extra water. Treating for bacteria only takes a short contact time.
Data per "Backcountry Water Treatment to Prevent Giardiasis" by JERRY E. ONGERTH, PHD, PE, published in the American Journal of Public Health (Am J Public Health 1989; 79:1633-1637.) They studied 10 minute contact times at 10C temperature differentials- no inactivation at 40C (104F), most Giardia Lamblia inactivated at 50C (122F), all Giardia types inactivated at 60C (140F). Unfortunately they didn't test for shorter contact times.Nov 29, 2009 at 8:57 pm #1548851
Denis HazlewoodBPL Member
@redleaderLocale: Luxury-Light Luke on the Llano Azul
I shut off the stove when a rolling boil is achieved. Never had a problem in the past 40 years.Jan 10, 2010 at 12:00 am #1561280
@b-g-2-2Locale: Silicon Valley
Everybody has addressed the normal issue of heating the water at normal elevations to achieve some safety. The problem changes somewhat at very high elevations. On a climbing expedition, we found ourselves camped just slightly below 20,000 feet. Our only source of water was to be from melting snow. However, the snow had all of these petrified artifacts from previous campers. If you check it, the boiling point of water (roughly 175 F) there was just about at the kill temperature for Giardia, so we had to be cautious. Despite the fuel rationing, we boiled the hell out of that water, and we did not get sick.
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