The pre-filter has a little velcro attachment on it that I always use to attach a small rock and submerge the pre-filter.
As far as freezing I have read that as well but once again I haven't had a problem. I backpack starting next weekend for Bear all the way through the end of November so I've hit some pretty cold temps.
im not even going to lie to anyone. the Katadyn Base Camp Micro Filter is by far the best filter system i have used......it is a little bigger but the amount of water and how fast you get water is unbelievable. it is more of a base camp filter, but it holds a lot of water and can just be opened up to fill bottles or fill up other "holding tanks".
the way four of us used it was to pack in a "holding tank", a collapsible plastic 5 gallon h2o container, and we just kept that full of clean water. we usually filled it once a day. plenty of water for 4 of us everyday. it was quick and the filter never clogged, but we did keep it out of the moss and vegetation. i would never go into the backcountry without it.....just saves a lot of time and energy. one or two times a day filling up the bag, and you have water for days. takes a couple of minutes to filter the bag full of water (about 2.5 gallons of water), is all.
its not as small and handy on the trail, but for over a week use.....you cant beat it. it will save you time and energy and you will always have more than one bottle of h2o on hand at all times.
Has anyone ever used the MSR MIOX system? Just curious what the thoughts are.
I use the Sawyer squeeze water filter. Light weight and works great. I also carry 2 of the bags for it empty just in case one leaks or I need to pack more water for some reason.
I'd recommend using the Katadyn Micropure water tablets, they are fast, effective, and pretty affordable. Also if you want to be extremely lightweight use a "steripen". The steripen is a water purifier that uses an advanced shade of light to take out the harmful contents in water. Just be sure to bring a few extra batteries in case they run out but the steripen has great battery life and can purify liters and liters of water.
I use iodine tablets, but am seriously considering getting a steripen.