I used the bottle all the way through the trip, from Kathmandu to the top of the Gosunkunda trek 4710 meters and back to Kathmandu. For a total of 26 days, it was faultless, and the flow rate never changed throughout. As with all these things its important from a hygienic/sickness point of view that these filtration systems work effectively and this day an age that we are not using plastic bottled water for these trips. As a rough estimate my bottle stopped about 140 plastic bottles been used and dumped in the mountains!
Ian Forbes, FRGS