Doug - a quick question: Are filter units (esp. thinking about ceramic filters) in any danger of being damaged by freezing? Not idle curiousity; I've often wondered what happens. Say I use a filter to replenish my water bottles and then stow it in my pack - in sub-freezing conditions. Filter elements would be wet from use. When the unit freezes, 1) is there any damage to the filter from expansion 2) next time I use the filter, is it going to be a pain to move water thru it until the durn thing "warms up" to the water temp or...??? Thanks in advance.<br><br>Tom