Are there any water filters that can be left in a car in the winter?

Seems like all of 'em stop working after one or two freeze / thaw cycles.

One that hasn't been used might survive, it's the water trapped inside freezing that cracks them.

The Sawyer Mini, unused, can survive freeze/thaw cycles undamaged. I believe that other Sawyer filters are the same.

Once they are used, it’s essentially impossible to get all the water out to prevent damage to the fibers if they are exposed to freezing temps again.

Ah. I wondered. I didn't know if they were somehow primed at the factory or something that would leave some trace of water present.

So, in the winter, they're essentially single use (or at least, until they freeze again). I can live with that.

Thanks.

My winter plan would be to keep my filter in my coat.

I'm still working out the details.

This is in the context of winterizing the car. I'm redoing the car's kit (all the stuff required by a car... shovel, fixaflat, cables, etc) and my kit (the Unplanned Hiking / Camping kit).

Ideally, I'd like to leave the filter in the bag and forget about it unless I need it. Like you suggest, though, once I do need it, I'll probably need it again soon after, so it makes sense to transfer it to an interior coat pocket.

I have a butane stove and metal nalgene bottle in there, so I could boil water, but I much prefer filtered.

just get a mechanical filter then?

Can you elaborate a little? I'm not sure what you mean by a mechanical filter. Even the grayl says not to let the filter element freeze.

I meant a pump ceramic filter that does not use hollow fiber technology. I was going to name the MSR Sweetwater, but that one may be discontinued. Maybe a Katadyn Hiker Pro or MSR Miniworks.

https://www.msrgear.com/water-treatment/filters-and-purifiers

https://sectionhiker.com/msr-miniworks-ex-water-filter-review/

When the ceramic filter is wet, freezing it still can cause cracks. It may be even more vulnerable than hollow fibre as ceramic is more brittle.