About 3 weeks ago, I bought an MSR Miniworks Water Purifier. I used it in the mountains two Sundays ago, and it seemed to work just fine. I took water from a lake and after I filtered the water (at about 1 litre a minute), I noticed that there were fish guts only feet from where I had collected my water. I drank that water with no ill effects that I know of. I am still alive, and figured that if I didn't get sick from drinking that water, I have no doubts that this filter will clean about any water I encounter. When I cleaned the filter out, I could see all of the junk that it filtered out. It was Amazing!!!