Menawa wrote: "Sure, if you reduce the pressure enough, water will boil at room temperature."

That's right. And the water that flashes into vapour should be extremely pure.

So how do we capture that vapour? I see some sort of crazy hand-cranked piston setup, with raw water in one vessel and drinking water condensing in another.

Seems like a lot more work than filtering, though.

BENJAMMIN--
is this what you were thinking of???
this is a homemade "fixture" for removing dents from Sigg
bottles..it's the cap with a bike valve glued in..



you put it on the bottle and pump up with a HAND PUMP and
the dents pop out..no it will no blow up..the gasket will
leak long before the bottle will fail..i get it up to 80PSI
with no problem and the Forest Service has tested the bottles
for use in aircraft and they fail only at very high PSI..
ANYWAY---could you crush the life out of the nastys in
the water by putting them under just the pressure you
could come up with in a home made gizmo ??? i think that
was the crux of Benjammin's question..



ACTION PHOTO...and please no "nannyism's" on this..
if you use a HAND PUMP the pressure will come up slow
enough that the cap gasket will leak and the bottle
will not blow up and cause you and your family,frends
and the health care system unnessary grief and expense..
thank you....

So I'm wandering, if you had a bike pump and pressurized it, at what pressure would you need to get it up to 212 degree and how long would you have to hold it to kill viruses? I would think the heat in the tank would convect out to the open air quickly once you came up to the temp/pressure not giving enough time to kill pathogens.That would probably be where vacuum jacket would help, but would crush under pressure. Force=Area(in Square inches)X Pressure. It would be interesting if you have a laser thermometer and measured the outside wall as you brought pressure up, and looked at how fast it dissipated.

CANOEDOGS - Not to nanny you here - and you may be sure that they'll never blow up - BUT *very* cheap insurance would be to mostly fill the bottle with water. Bonus is that you won't have to pump as many strokes.

Gotta agree with thseng--liquids are, for all practical purposes, incompressible. That's how we can take advantage of hydraulics.

But, an interesting idea. Benjammin, please don't go and hurt yourself with that fire piston. Seriously--you won't be boiling any water with it!

THSENG..
these are photos i took for another campers site a few
years ago..i tryed filling with water first but could only
pump a few times before it became to hard to do..then i tryed
them dry and it was pumping up a bike tire and the dents
"crinked" out..i also did stuff like put a wet rug over the
bottle for a "blast mat" but found that was not nessary.

Uhhhhhhhh... A pressure cooker RAISES the boiling temperature so that you can get the temperature of the food or water ABOVE 212F(100C)...
At high altitudes, you have to use a pressure cooker just to make sure that your food reaches a safe temperature, or that your water is sterilized... It is not the boiling that cooks or sterilizes, it is the temperature... And you can not get the temperature of something(in it's liquid state) above it's boiling point. So you have to raise the boiling point to a point where the temperature is high enough to cook or sterilize...

> Pressure Cookers: boil at lower temps.
Hmm... . My thought was that water under pressure boils at higher temps. Hence pressure cookers for canning reaching higher temps than 212 to sterilize the food better, quicker, or whatever.

Cooking at high altitude requires different times because water boils at less than 212 degrees, right?

I am pretty sure the pressure alone will not be enough to get water to boil. As someone mentioned, water is incompressible, so putting it under extreme pressure will not do much. We used to test high pressure tube fittings at up to 6000 psi, filled to the top with water, with no noticable change in the temperature. This prevented an potentially deadly explosion, because a if a device was filled with air at that pressure, the expansion of the air would cause a huge BOOM! and probably kill anyone nearby. Filled with water though, it's more of just a small harmless pop because there is much less air volume to expand.

The other factor that needs to be considered is high heat capacity of the water and the amount of time it takes to bring up that pressure. The reason those fire pistons work is because the volume of tinder is very small and they compress the air in a very short amount of time, thereby increasing the pressure and temperature very rapidly. If you try and slowly pressurize it, most of the heat generated will quickly dissapate through the walls of the chamber. You could increase the temperature of the water using the pressure/temperature principle, but the I'm guessing it would be very inefficient. It would probably be the same effect as using water to cool the heatsink fins generated from an air compressor. Water is able to absorb a tremendous amount of heat, which is why it is used in everybodys radiators.

The microbes would be sustained in the droplets of vapor. The only way to do it would be to drop the pressure to the point that they explosively decompress, and if you have the omphy of a vacuum pump, you're not that far into the back country.