Hydrapak Seeker+ 3L Filter Kit

What it removes from water, and how well that is proved. 8: Clearly better than most.

0.2 µm hollow-fibre filter cap. HydraPak's fact sheet, linked from its UK product page, names the EPA Guide Standards and NSF P231 for bacteria and cysts: a named standard for bacteria and protozoa, so 4. The product page gives a lower E. coli figure and cites HSF 42, so we use the fact sheet. No virus claim. OutdoorGearLab reports SGS Labs tests of the Flux+, which has the same 42 mm filter cap: over 99.9% of bacteria and protozoa removed and 29.5% of viruses.

How fast clean water comes through when it is new. Real flow drops as it clogs: see Ease of use. 4: A bit below average.

HydraPak gives only a minimum, "more than 1 L/min", on its page and fact sheet. We band the figure it gives, 1 L/min, which is 0.6 to 1.19, so the real score could be higher. Better Trail found the claim about right for a new filter and says its two-year-old filter stays close to 1 L/min if soaked between uses. OutdoorGearLab took 28 to 38 seconds a litre on the Flux+, which has the same cap (1.6 to 2.1 L/min). Banded on HydraPak's figure.

How much it adds to your pack. 7: Better than most.

127 g for the 3 L bag and filter cap (HydraPak), in the 90 to 149 band. Ultralight Outdoor Gear lists it as 127 g without the stuff sack.

Filling, squeezing or pumping effort, how fast it clogs in peaty or silty water, and how easy it is to clean. 8: Clearly better than most.

Bikepacking.com (3) used this 3 L bag with its filter cap for about two months: simple, though water needed some pressure to go through, and it rinses clean by swishing. Better Trail (5) tested the same 42 mm cap on soft flasks, and OutdoorGearLab (4) tested it as part of the Flux+ bottle: little learning curve, no backflushing but a swish-and-soak clean. Those two reviews cover a different bottle, so we count only what they say about filling through the cap, squeezing and cleaning it, not the bottle or the 3 L bag (the same rule as the Platypus QuickDraw and Katadyn BeFree files). OutdoorGearLab's score covers the whole Flux+, so it is the weakest of the three. Average 4 out of 5, so 8 out of 10.

Reviewers disagree on this.