Filters I must admit that prior to picking up my Katadyn filter in Damascus I occasionally drank untreated water. I must also admit that I arrived in Damascus with backpacker's diarrhea. I didn't know much about them, so I selected based on small pore size and figured that higher price meant better quality. Several other hikers reported similar results. There are about 15 models available, many of which are sold by REI, which publishes a table giving information about comparative performance.
All outputs are about the same.
Filter composition is hard to compare. Although I have listed these in my order of preference, choice among them is difficult and must be based upon personal preferences. I believe that PUR and MSR are effective against Giardia, although they were not tested in the field by Ongerth. Several hikers told me that the inexpensive First Need broke down after only moderate use, and Ongerth suggests that it has a useful life of about 800 pints. Work Outdoors at GORP Jobs Click Here.