Have been using a katadyn pocket filter for over 10 years now, so I know their ceramic technology well. I'm pleased to see they've adapted their siphon filter unit to be used in conjunction with a 10L ortlieb water sack. The performance is rated at 5L an hour, while suspended 1.5 M above the point of collection. I know from using the pocket filter just how much effort is required to pump 5L, although this can be done in less than 10 minutes. There are definite advantages to using a gravity filter, no moving parts to wear out, and no effort, just patience. If this filter idea is as good as it says it is, I'm definitely going to try it, since the 10L water sack is part of my standard kit anyway. If anyone else has tried this arrangement from katadyn I'd be interested to hear how you got on. Here's a link to their site.<br><br>http://www.katadyn.net/katadyn_camp.html<br>

In conjunction with the use of a siphon filter, does anyone have any good ideas to seperate mud and scum from water, prior to filtration. Does stirring sand or clay into muddy water help the mud to settle at the bottom quicker? Just a thought.

I've used a simple uncoated nylon stuff sack. An item most campers or backpackers have anyway. Fill it up with water and let the strained water drip into a container for iodine treatment or hold the bottom of the sack under water and allow the water to seep in to act as a pre-filter for mechanical filtration.

Adding clay or sand will just give you more lithics to settle. A large square cloth ( such as a bandanna) makes an expedient filter for the big stuff. Or, you could pursue the macho image of some survivalists and strain it through your teeth ( I've seen other web posts debunking mechanical filters as no more than sales hype.)

My experience with gravity filters is with the larger group units for stationary camps or disaster scenarios. They are simpler and can be left to passively filter while you perform other tasks.

If you have the time, simply letting the mud settle to the bottom and then decanting the clearer water from the top of the container works quite well. I used this technique, followed by boiling, in some really contaminated water for about a month and it worked very well (no sickness and I am still here). This was before the days of mechanical filters.