When a liquid is chilled below it's freezing point, it's called supercooling. A liquid can also be heated above it's boiling point, and it's called superheating.
I'm not sure how water in a stream manages to get supercooled, because the typical way to supercool water is to place pure water (such as obtained by distillation or reverse osmosis) in a smooth container and place it in calm below freezing conditions. Once the water is supercooled, you can instantly freeze it by tossing something into it.
Superheating is something you have to be careful about with microwave ovens. If you place water (and it doesn't have to be pure water) in a smooth container an microwave it, it is very easy to get part of the liquid to be superheated. When you then add something to the water, the superheated parts of the water will instantly vaporize splashing scaling on you.
I've mostly switched to aqua mira for winter time. It's just easier to deal with than a filter. I use either nalgene or Gatorade bottles in the winter which makes it easy enough to deal with, just dunk then wide mouth bottle in the watersource, mix the chemicals wait a few minutes and mix. I stopped using my camelbak in the winter since the hose and threads freeze until too easily.
For what it's worth, I've used the sawyer squeeze in the winter on numerous occassions. It's quite manageable to keep it from freezing, but it's also a pain in the arse to deal with filling the filter bags and sit there squeezing it with bare hands.
Colorless green ideas sleep furiously.
A quick take on moving water in the Appalachians.
https://www.google.com/amp/s/walterh...in-winter/amp/
Pay no attention to the salamanders.
Wayne
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Eddie Valiant: "That lame-brain freeway idea could only be cooked up by a toon."
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I used a Kathryn pocket and pumped it dry sideways. I had a couple of issues with small amounts of water freezing, but thawed it on top of my pot, with some snow inside to make a double boiler. The few times I had to melt snow (which takes huge amounts of fuel) I didn't bother boiling fully. The snow was fresh. The filter worked well even when pumping a trickle off the top of ice.
However, I had a particularly bad year on the AT. Chances are that if keep your filter in your jacket, sleeping bag, or buried in your pack it won't freeze. Drink lots of water as it helps prevent hypothermia and frostbite.
Has DW been making his/her fantastic claims yet again? It's either his/her imagination, or a busted thermometer.
Under high pressures, of course, ice turns to water, even well below 32 degrees, it's why ice is slippery, a by product of the water-unique property that is actually expands when it freezes.
Out in the field, water just plain doesn't exist in liquid form when its temperature is below 32F. Or show me a valid reference to the contrary. After seeing the claims already made in this thread, I started to have a glimmer of doubt, so I did verify to myself I wasn't having an O.L.D. attack ( a common occurrence these days), and found plenty of references that in this case I wasn't.
In any case, sounds like original question resolved, no Sawyer to be used in extreme cold conditions, which is wise. Do keep in mind though, melting snow/ice for water does take a lot of extra fuel, so plan accordingly. The mountaineering rule of thumb for carrying fuel on extended winter trips is 8 ounces of fuel per person per day. I have done dozens of deep cold and sometimes extended (2-3 week) cold trips and found this rule of thumb to be extremely conservative. My own rule of thumb is 6 ounces per person per day, and have found even this to be conservative, the real number being more like 5. So we carry 6 to have some margin. I'm talking about either canister fuel or white gas, both have just about the same energy per ounce. These rules of thumb assume all your daily water comes from melting snow. Thankfully many times you can indeed find flowing streams in the dead of winter.
Sorry folks, again, liquid water below 32 degrees exists only in extreme circumstances, certainly not in mountain streams. Google up "super cooled water" and check things out.
Just want to point out... Even with 32F water coming from a running source, as soon as you bring that out into the 10F atmosphere and increase the "surface area" of the water by squeezing it through tiny tubes of the filter, I would expect it to freeze very readily... No?
I'm planning on an early March start... I think my plan is to use the Sawyer as normal if temps are above 32F, and just drink untreated/unfiltered water if it's colder than that. Yolo?
I have never used a Steri-Pen as a single source of water treatment, but rather as a way of treating water quickly on trail when I come to a water source and want to camel up and not carry a lot of water. When used this way I can go 10-14 days on trail with one set of batteries. In warm weather I have used a Sawyer Mini for the same purpose. I tend to use Aqua Mira to treat water in camp. The SteriPen folks will have information on how much water you can treat on a set of batteries. One tip: always remove your batteries when storing the SteriPen.
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You are wrong. Science is right. I'm going by the fantastic idiotic? unfounded? claims of the scientific community who are more interested in facts than your feelings or personal beliefs or what you sense or mythology. Why attack me? You attack my findings? What did I have a broken thermometer? You try to belittle me? Jag off. Go attack science that says liquid water can certainly occur at temps well below 0* C IN THE FIELD!
http://www.smithsonianmag.com/scienc...reeze-1120813/
http://io9.gizmodo.com/5862789/whats...turns-into-ice
https://www.sciencedaily.com/release...1123133123.htm
Dogwood,
Come on man!
3 references to the same laboratory experiment?
No worries.
What we need is a reasonably accurate thermometer, a mountain stream and the ambient temperature below freezing for a few days.
Surely some of the mountain dwelling members here can help us out. Rob? You're nominated.
Lol!
Wayne
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Eddie Valiant: "That lame-brain freeway idea could only be cooked up by a toon."
https://wayne-ayearwithbigfootandbubba.blogspot.com
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I'm declaring shenanigans