Method 1: Boiling
Boiling is the most reliable way to make unsafe water safe to drink.
Steps
- Bring water to a rolling boil (you'll see vigorous bubbles appearing at the centre of the pot)
- Keep boiling for:
- 1 minute at sea level
- At least 2 minutes if you're above 2,000 metres elevation
- Let it cool before drinking or storing
- Store in clean containers with lids
What it kills
- Bacteria
- Viruses
- Parasites (protozoa)
What it does NOT remove
- Sediment or cloudiness
- Chemicals
- Heavy metals
Method 2: Bleach disinfection
If you don't have a pot or fuel to boil, use unscented household bleach.
Steps
- Use only unscented bleach with 5.25% sodium hypochlorite concentration
- Add 2 drops of bleach per 1 litre of water
- Stir well to distribute the bleach
- Wait 30 minutes before drinking
- Check the smell: The water should have a faint chlorine smell
- If it doesn't smell like chlorine, add 2 more drops and wait another 30 minutes
What it kills
- Bacteria
- Viruses
- Most protozoa
What it does NOT remove
- Sediment or cloudiness
- Chemicals
- Heavy metals
Important
Do not use bleach with added colours, perfumes, or surfactants. Only plain household bleach works for water disinfection.
If water is cloudy or discoloured
Before boiling or bleaching:
- Let sediment settle for a few hours if possible
- Carefully pour the clear water into a clean container, leaving sediment behind
- Filter through a clean cloth if needed
- Then boil or bleach as described above
Filters and other methods
Many types of filters exist (squeeze, gravity, ceramic, hollow-fibre). Most remove bacteria and parasites but NOT viruses or chemicals. Check the product label for what it removes. Filters work best combined with boiling for complete safety.
See also: What to do during a boil-water advisory for official guidance if your local water supply is affected.