Cold Weather Effect on Water Bottles & Filters

This is a trick question, right?

When the air temperature dips to the freezing point of water is when freezing problems start up in the filter.

You can change that freeze point by using some medicinal alcohol as an antifreeze solution.

–B.G.–

32 degrees farenheit ; ). Remember that allowing a filter membrane to freeze may damage the filter and allow larger than pore size particles through the membrane.

Dancer,
Not sure exactly what you are looking for but I'll offer a couple suggestions.
The colder it gets the harder it is to keep water from freezing.
Keep your filter from freezing (below 32F/0C) as this will likely damage its capability to deliver clean water. Keeping it inside the tent and/or sleeping bag during the night is one suggestion. Keep it insulated and inside the pack during the day.
If its really cold consider an alternative purification method.
Same basic idea with water bottles. Insulate and keep inside.
Many folks will use wide mouth bottles rather than narrow like the platy in freezing conditions. The narrow opening is more likely to freeze more quickly.
You can carry and store the water bottle upside down as the water tends to freeze from the top down.
Insulating bottle covers are available for some popular bottles, like the wide mouth 1L Nalgene. Or you can make something yourself.
Does that help?

go insulated or carry the water close to yr body if it gets really cold

carry the filter inside yr jacket … of filter by chemicals/boiling

nalgenes come into their own at these temps … you can fill them up with hot water in the morning …. and use insulated sleeves

more info: I am backpacking this weekend and the nightime temps will be below freezing. I did not have to worry about this when I used nalgene bottles I just turned them upside down. Do gatorade bottles work Ok in these conditions..I do not want to carry the extra weight of nalgene bottles or insulation if I can avoid it.

When I go snow camping, I use a variety of water bottles. During the daytime when the temperature should be above freezing, I keep each bottle in a near-black plastic bag (trash bag material). Sunlight keeps that warmed up more, so at night after the temperature drops, it never quite freezes over.

–B.G.–

If I understand your question right, you are going to be using Gatorade bottles? Are you planning on filtering your water before bed and letting them sit out overnight? If you do that you could instead bring the bottles with you in your sleeping bag overnight (make sure they're leakproof). Or filter in the morning. You could also heed Bob's advice on mixing in some alcohol (food-grade not denatured!) and thus reduce the freezing point. When hiking in cold conditions, I've yet to have a bottle freeze as the sloshing motion keeps it liquid.

Besides, if you get the right mixture of alcohol and water, the bottle may freeze, but you won't care.

–B.G.–