What did you do to keep water filters from freezing

[Cookerhiker]

When I used a filter, I drained it and put it in my sleeping bag. Now I use a steripen.

[Snowleopard]

When I used a filter, I drained it and put it in my sleeping bag. Now I use a steripen.

Winter seems like the time when a steripen has the advantage over filters and chemicals.
Filters may freeze.
Chemicals take longer to work in cold temperatures.
Are there any problems with using a steripen in cold weather?

[Vibe]

I'm a bit surprised that no one has suggested flushing the filter with drinking grade ethanol - as both a disinfectant and an antifreeze.

[ChinMusic]

Are there any problems with using a steripen in cold weather?

Only if ice is present. UVC will not penetrate ice.

The temperature of the liquid water has no affect on the effectiveness of the Steripen.