Okay, I got my Sawyer Squeeze. Unfortunately, it says if it freezes you have to discard it.
If I have to keep it from freezing, it is quite limiting because maybe 1/4 my trips go below freezing at some point.
I emailed them and they replied:
"The fibers are made of a polysyphonic extrusion. It is in the nylon family but much tougher. If a droplet was to freeze inside of one of the filters 0.1 micron holes can it expand and stretch the hole size? We don't know and there is no way to test it conclusively. So our position is to play it safe and say no freezing. Allowing the filter to freeze will void the warranty. If it is accidentally frozen then we suggest using it until you get home and can replace it."
Nylon is a bit stretchy, so it doesn't seem like it should be a problem.
The problem with broken water pipes, is when a run of pipe freezes from one point to a closed point, like a faucet. It expands down the run, and when it gets to the faucet there's considerable pressure and it can break. If you have a droplet inside a pipe, it's not a problem.
If the 0.1 micron hole got expanded to 0.2 microns, who cares?
Besides, this is all placebo anyway, water doesn't need to be treated : )
It seems like this could be tested. Freeze a filter. Look at holes with microscope.
Or take a solution with flourescent particles that are 0.2 microns and see how many get through.
Compare filter that was frozen with one that wasn't.
