Water
Water Purification
Make any water source safe to drink
Why Learn This Skill
You can survive roughly 3 days without water. Every natural water source harbors pathogens, heavy metals, or chemical contaminants. Knowing multiple purification methods ensures you have a backup when one fails.
Step-by-Step Guide
Boiling
Bring water to a rolling boil for 1 minute (3 minutes above 6,500 ft elevation). Kills all biological contaminants. Does not remove chemicals or heavy metals. Best when you have fire and a container.
Filtration
Pass water through a quality filter (Sawyer Squeeze, LifeStraw, Berkey). Removes bacteria, protozoa, and sediment. Most modern filters have 0.1 or 0.2 micron pores. Pre-filter cloudy water through cloth first.
Chemical Treatment
Use water purification tablets (iodine or chlorine dioxide) or unscented household bleach (8 drops per gallon for clear water, 16 for cloudy). Wait 30 minutes before drinking. Chlorine dioxide tablets are most effective against Cryptosporidium.
UV Treatment
A SteriPen or similar UV device destroys the DNA of pathogens in 60–90 seconds per liter. Requires batteries. Very effective but does not remove particulates — pre-filter cloudy water first.
Solar Disinfection (SODIS)
Fill clear plastic or glass bottles with water, leave in direct sunlight for 6 hours (or 2 days if cloudy). A slow backup method when nothing else is available.
Pro Tips
- Always pre-filter cloudy or silty water through a cloth or coffee filter before using chemical treatments or UV — turbidity reduces effectiveness
- Combination is best: filter first, then chemical treat or UV for double protection
- Store purification supplies in your vehicle, BOB, and home
- Know the contamination type in your area — filters handle biologicals, distillation handles chemicals
- Unscented household bleach (5.25–8.25% sodium hypochlorite) is an effective emergency option
Common Mistakes
- Using only one purification method and assuming it handles all threats
- Forgetting to treat the container as well as the water
- Using scented bleach for water purification — toxic additives
- Relying on UV treatment for turbid water without pre-filtering
- Not testing your filter before you need it in the field
Recommended Tools & Gear
Related Threats
Scenarios where this skill is critical.