Gear School: Water Filters

Remove most micro-nasties, draw water from barely-there puddles, and quench thirst fast with the versatile pump filter.


  • Extend cartridge life and preserve flow rate by drawing from the clearest possible water sources: calm pools, rocky streams, and headwaters. Avoid algae-filled ponds and turbulent, silty streams.
  • If you must filter dirty water, prevent clogging the prefilter and cartridge by wrapping a coffee filter or bandana around the prefilter with a rubber band.
  • Never allow water to freeze inside the filter, as ice can rupture fragile cartridge components. Pump all water from the cartridge before packing it away.


  • Ceramic or silica depth filter: When you notice diminished output, remove the cartridge from the filter housing (take care not to drop it–ceramic cracks easily) and scrub the outer layer with a cleaning pad (generally included; use fine steel wool or sandpaper if not).
  • Pleated filter (or filter cover): Remove from the housing and swish it around in clear water to rinse away surface sediment.
  • Hollow-fiber filter: Backflush after each trip by reversing the direction of water flow. Unscrew the inlet cap, flip over the check valves, and pump a half-liter of filtered water through the cartridge to clean it (see product manual for complete instructions).
  • Disinfect all filters at the start and end of each season by pumping one capful of bleach mixed with one liter of water through the cartridge (use just a few drops of bleach for hollow-fiber models). Disassemble the filter and let all components dry completely.


  • Pump not drawing water? Try turning the housing upside down and pumping again; that often gets it going.
  • No luck? The problem is probably dry, cracked, or dirty O-rings. In the field: Remove O-ring from the piston, clean with a soft cloth, and lube with silicone grease, lip balm, or saliva. At home: Replace damaged or worn O-rings.


The cartridge contains tiny pores (.2 microns or smaller is standard for backcountry use) that let water pass through but block protozoa (Giardia, cryptosporidium) and bacteria. Consider these major types:


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