Katadyn BeFree 1L
0.1 micron, collapsible 1 L flask, ~63 g
4.6 on Amazon
The fastest flow of any soft-bottle filter and it collapses to nothing when empty — the flask is the weak point, and a pinhole in it ends the system rather than the filter.
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Do not buy this if: Rough handling in a duffel. Take the Sawyer if your kit gets thrown around.
Not every route needs it. These are the ones where our guides would put it on your list.
Everything else we recommend in filters & purifiers, including the ones we think suit a different trekker.
Best overallSawyer Squeeze Water Filter
Effectively unlimited water for the cost of a couple of bottled waters, and it threads straight onto a standard bottle — it does NOT remove viruses, so pair it with chemical drops on trails below villages.
The virus half of the answerAquatabs Water Purification Tablets
Handles the viruses a filter misses and weighs nothing, which is why we recommend carrying both — it does not touch cryptosporidium, and it makes the water taste of a swimming pool.
Simplest complete answerGRAYL GeoPress Purifier
The only single item here that removes viruses as well as everything else — you pay for it in weight, in cost, and in a cartridge that needs replacing every 250 litres.
