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SESK: Stuff Everyone Should Know · sesk.info/hike-water-filter

What does a filter with an absolute pore size of 1 micron or smaller remove?

Parasites like Giardia, but not viruses or all bacteria.

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  1. Salt from seawater
  2. Viruses
  3. Parasites like Giardia ✔

Why: CDC says a filter with an absolute pore size of 1 micron or smaller removes parasites like Giardia, but not viruses or all bacteria.

Huh, didn't know that: A filter with an absolute pore size of 0.3 micron or smaller also removes bacteria, but still not viruses.

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Why did the water filter break up with the virus? It said you are too small for me.
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References

Answer: Parasites like Giardia. CDC says a filter with an absolute pore size of 1 micron or smaller removes parasites like Giardia, but not viruses or all bacteria.

  1. CDC: Water Treatment When Hiking, Camping or Traveling www.cdc.gov/drinking-water/prevention/water-treatment-hiking-camping-traveling.html
    A filter labeled with either of the following will remove parasites, but not viruses or all bacteria: Absolute pore (hole) size of 1 micron or smaller
    Checked 2026-10-12.
  2. CDC: Water Treatment When Hiking, Camping or Traveling www.cdc.gov/drinking-water/prevention/water-treatment-hiking-camping-traveling.html
    A filter with an absolute pore (hole) size of 0.3 micron or smaller will remove bacteria and parasites, but not viruses.
    Checked 2026-10-12.

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