I think the 30 L/hour that REI is quoting would be very optimistic. Maybe with a brand new filter element and tap water you could get that flow rate, although I doubt it on a gravity fed system. I think the 5L/hour that Katadyn quotes is more likely reality. I have the old Katadyn Guide model filter, and it seems to do about what they quoted on the materials that came with it, even after the filter has been used for a while, so I'd feel more comfortable with their numbers.
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- Ron