One point to consider regarding use of water filters in cold weather: Both Sawyer and Lifestraw warn that once their filter have been used, they should not be exposed to freezing temperatures. Ceramic filters are not as susceptible.
From the Lifestraw web site: “If your LifeStraw has been used, and is then exposed to freezing temperatures, water inside can freeze and crack the filter. You may not see these cracks, so we recommend never letting it freeze once it’s been used. When camping at high elevations or freezing temperatures, be extra careful not to let it freeze.”
From Sawyer web site: “Before initial wetting Filter is safe from freezing temperatures if it has never been wetted. After initial wetting While there is no definitive way to tell if a filter has been damaged due to freezing, Sawyer recommends replacing your filter if you suspect that it has been frozen. During trips If you are in freezing temperatures, we recommend that you store your filter in your pocket or close to your person so that your body heat can prevent freezing. There is no warranty for a frozen filter.” [Emphasis added.]
I contacted Katadyn and asked if the use of the Pocket or Ceradyn in freezing temperatures would damage the filters. I received the following response:
“Only if you try to run water through the ceramic elements before they have thawed out. And in the case of the Ceradyn, if you have water in the upper chamber and it freezes and cracks the ceramic elements. When not in use, both units should have excess water either pumped out (Pocket) or poured out (Ceradyn) if you are in freezing conditions.”
Sincerely, – A Reader