In thinking about a longterm survival situation, I realize that no matter how much water I store, the supply can run out. When the supply runs out, finding a source of clean water may not be possible. If I hunker down at the house, I may need to take some water of which the quality is unknown, and use it.

So, I have been thinking about a system that I could build that would provide a good supply of clean water. In my thinking, I would probably want to work in stages.

My first stage would be a tank with two outlets, one at the very bottom and another some distance off the bottom. Put water into this tank, let sediment, etc. settle out of it and.or rise to the top, and draw water off from somewhere in the middle.

My second stage would be to try and filter it through sand. Slow sand filters are used in third-world countries to supply clean water. But, I really have no idea about using one of the filters that relies on biological growth near the top to clean water. I would probably build a couple boxes, fill them with sand, and use one at a time to seep the water through.

My next ideas would be to filter it again, possibly through carbon. I know activated carbon can remove a lot of chemical impurities, but sooner or later my supply of activated carbon would run out. What would happen if I made and used my own charcoal for a filter?

Finally, chemical treatment seems to be an ideal final step. Preferably with iodine, but if not, then chlorine.

Are there any steps or stages you would consider changing, adding, deleting? There is a stream of running water not far from the house, but as I would not want to use it without treatment. If possible, I'd like to design a system to use as little stored resources as possible. If a syastem can use things you can readily obtain without buying, then it seems to me that is an ideal renewable system in a longterm situation.

Thanks.