Making water safe to drink
Boiling, chlorine, filter, sun: what kills what
Boiling
- 1 minute at a rolling boil kills everything
- 3 minutes above 2 000 m altitude
- Microbes die as low as 60-70°C
- 10 minutes = useless waste of fuel
Chlorine (unscented bleach 5-9%)
- 2 drops per liter of clear water
- Double the dose if cloudy, colored, cold
- Stir, wait 30 minutes
- A faint smell of chlorine should remain
- An old bottle loses strength within 1 year
Iodine and chlorine dioxide
- Iodine 2%: 5 drops/L, 10 if cloudy, 30 min
- Iodine not recommended if pregnant or thyroid issue
- Chlorine dioxide: the only one to kill cryptosporidium
- Cryptosporidium: 4 hours of contact time required
Filter (Sawyer, LifeStraw)
- 0.1-0.2 micron: bacteria and parasites, yes
- Viruses: no pocket filter stops them
- Combine with chlorine in viral risk zones
- Freezing destroys the filter's hollow fibers
SODIS (sunlight)
- Clear PET bottle, 2 L maximum
- 6 hours of direct sun, 2 days if overcast
- Test: read a newspaper through the bottle
- No effect on chemical pollutants
In order
- Choose the least bad water source
- Decant or strain through tight cloth
- Disinfect: boiling, filter+chlorine, or SODIS
- Do not recontaminate the container after treatment
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