Boil and basic cloth filtration — zero-cost emergency method

When no equipment is available, cloth filtration followed by a rolling boil is the oldest and most reliable method to make any water safe for drinking. It eliminates all biological pathogens at zero cost.

Steps

1. Pre-filter through cloth: Pour rainwater through a clean cotton cloth (t-shirt, bandana, or pillowcase) folded 4 times. This removes sediment, insects, and large debris.
2. Bring to a rolling boil: Heat the filtered water to a full, vigorous boil.
3. Boil for 1 minute: At elevations below 6,500 ft, 1 minute of rolling boil kills all bacteria, viruses, and parasites. At higher elevations, boil for 3 minutes (lower boiling point).
4. Cool and store: Let cool in a covered, clean container. Use within 24 hours or transfer to a sealed bottle.

Why It Works

Boiling at 212°F (100°C) denatures proteins in all known waterborne pathogens. The WHO, CDC, and EPA all endorse boiling as the single most reliable field water purification method.

Tips

• Boiling does not remove chemical contaminants, heavy metals, or dissolved minerals
• Let boiled water cool naturally — do not add ice (ice may be contaminated)
• In a power outage, a camp stove, wood fire, or rocket stove all work — the heat source does not matter, only the temperature