Good advice, thank you. Heading up to overnight Whitney sept 24 and lows at night are dipping in the mid 20s. Was a bit concerned about that happening. My line froze once for me on Baldy but it was a day hike and eventually the line cleared. I guess my best bet will be to empty the bladder and pump in the morning. I guess sleeping with the filter in my sleeping bag is the way to prevent it from freezing. Or not filter....
Cody
