OK I have briefly asked and some have briefly answered about urban water gathering. Basically I live in a very populated (sub)urban area. When one thinks of filtering water, we think of pumping the filter on a nice stream on a day hike...<br><br>My dilemma is that in the city, the river (basically, a concrete ditch with some moss on the bottom) isn't the best place to get water from. <br><br>After a major disaster (earthquake, in my parts) should I assume that the water lines may be compromised, and that I should treat the stuff coming out of my sink as suspect? If so, how would I clean it to drink it? Would a Katadyn filter do, or would my considerations be different? Iodine tabs?<br><br>What about terrorists or disgruntled water works worker poisining the water supply (becoming less and less unlikely, but say I'm Gen Ripper from Doc Strangelove and I suspected water tampering) could I assume the Katadyn would kill all the microscopic bad guys, or are they mainly designed for hiking/camping use?<br><br>Hope this makes sense and I don't sound too paranoid. IMO my needs may be different from those who see heading to the wilderness as a viable reality...I don't...it took me 4 hours just to leave the city on a camping trip fighting the Friday traffic out of LA....

When I need to be really sure that the water I am drinking is free from bugs and germs and other little nasties, I boil it. I don't boil for a long period, just get it to a nice rolling boil and then use. I have successfully treated some very ugly water sources this way. I stockpile genrous quantities of fuel, mostly propane, for this eventuality in an emergency.<br><br>A few years ago, the city fathers announced that, effective immediately, tap water should be boiled. It was an interesting experience. The stores immediately sold out their water supplies. We were able to boil all we needed for consumption - the incident complicated life for a bit, but everything worked out fine.<br><br>I would make the working assumption, following an earthquake, that water supplies would not be potable, and I would boil, whether or not the authorities made an official announcement.<br><br>Interesting experience you are having with the commercial 2.5 gal containers. I have never felt that they were very suitable for storage. In an emergency, I would boil the "moldy" water and use it. If I had better water, I would use it first for drinking.<br><br>I have a filter, and I use it often when backpacking. In my experience, they work fine when you are concerned with giardia and other bacteria. Some models, with silver iodide, are apparently effective against viruses. In a tough situation, like an urban disaster, boiling is simpler and protects against a wider range of problems.<br>

In the really nasty refugee camps that the Red Cross and Peace Corp operate in they often use something akin the Katahdyn Gravidyn filter (or so I'm told). I would think that if it works there where the latrine is an open hole or less then it should work in most places. I agree with Don on the boiling. I would filter and then boil. The boiling will get rid of most if not all bio hazards but not do a thing against some of the nastier HazMat problems. A decent activated charcoal filter will rid your water of most HazMat problems but do a mediocre job on the bio-nasties. The Katahdyn Gravidyn comes with silver impregnated ceramic and an activated charcoal core. This combination will filter out almost everything. Anything that comes through that can be killed very effectively by boiling. By this process you should approximate distilled water nicely from almost any source. Of course if you are truely paranoid the reverse osmotic filters are the most expensive and they usually require power. <br><br>If you are preparing for being in a house or car for the duration of a 72hr interruption of normalcy then I would expect that you could store the required amounts of water with little difficulty. If you are on foot in refugee status then a pocket filter with iodine tablets is all you are likely to be able to carry aside from your canteen (whatever size it is). that should be good enough if you stay away from raw sewage or industrial waste.