You need a water filter if your stored water supply runs out before normal services are restored, or if you're evacuating and can't carry enough water. The goal isn't to filter water every day — it's to have the capability when you need it.
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What to Look For
- Filter rating — look for filters rated to remove bacteria and protozoa (Giardia, Cryptosporidium) as a minimum. Virus removal is important for international travel or sewage-contaminated sources.
- Capacity — how many gallons can it filter before needing replacement? A Sawyer Squeeze filters 100,000 gallons; a LifeStraw personal filters around 1,000. For household use, higher capacity is better.
- Flow rate — how fast does it filter? Gravity filters are slow but require no effort. Squeeze filters are medium. Pump filters are fastest.
- Packability — for a go-bag, weight and size matter. For home use, a larger gravity system makes more sense.
- Ease of use under stress — complicated systems fail under pressure. Simple squeeze filters are hard to use wrong.
What to Avoid
- Filters that only remove taste/odor (like Brita) — these are not designed for microorganism removal
- Unverified filters from unknown brands — check for NSF/ANSI 42 or 53 certification, or independent testing data
- Expired filters or filters stored improperly after freezing (ice can damage filter membranes)
- Assuming any single filter removes viruses unless specifically rated for it
Related Guides
Water Guide
How to Store Water for Emergencies
72-Hour Kit
72-Hour Emergency Kit Guide
Checklist