When to Boil Water vs Use a Filter
Decision flow for boil-water advisories, camping filters, and household backup — sourced from CDC guidance.
Quick decision
| Situation | First choice |
|---|---|
| Boil-water advisory | Boil or bottled water from safe source |
| Backcountry stream (viruses possible) | Filter rated for viruses or boil |
| Household backup when power out | Boil if gas/electric stove works; bottled reserve if not |
| Chemical spill reported | Follow official instructions — filters may not help |
Filter limitations
Hollow-fiber camping filters excel at bacteria and cysts. Viruses are smaller — CDC recommends boiling, reverse osmosis, or filters explicitly certified for viruses when that risk exists.
Practical household stack
A practical backup order: stored bottled water → boil → rated filter + disinfectant per label → never guess on chemical contamination.
Key takeaways
- Advisories mean boil unless officials say otherwise.
- Match filter capability to the threat (biological vs chemical).
- Keep fuel or stove access in your power outage plan.