Water Purification
Water Purification
TL;DR — The 60-Second Version
You will die in 3 days without water. You can survive weeks without food, but dehydration kills fast. Finding and purifying water is your #1 priority after immediate physical safety.
The golden rule: If you didn’t purify it, don’t drink it. Clear water ≠ safe water.
Fastest methods:
- 🔥 Boiling — Rolling boil for 1 minute (3 min above 2000m). Works against everything biological.
- 💊 Chemical — 2 drops bleach per liter, wait 30 min. Lightweight and effective.
- 🔧 Filter — Ceramic or activated carbon removes bacteria and protozoa. Won’t remove viruses alone.
Why This Matters
Water infrastructure is the first thing to fail in any collapse scenario. Municipal water treatment plants require electricity, chemicals, and trained operators. Without any one of these, tap water becomes unsafe within hours.
The math is brutal:
- Average person needs 2-3 liters/day minimum (more in heat or exertion)
- A family of 4 needs 8-12 liters/day just for drinking
- Add cooking, hygiene, and first aid: 20+ liters/day per family
- Stored water runs out fast — you need to know how to source and purify
Finding Water Sources
Surface Water (Rivers, Lakes, Streams)
Most accessible but most contaminated. Always purify. Look for:
- Moving water over still water
- Water upstream of settlements
- Springs emerging from hillsides (often cleanest natural source)
Groundwater (Wells, Springs)
Generally cleaner than surface water but not guaranteed safe. Dig at least 50 meters from any latrine or contamination source.
Rainwater Collection
One of the cleanest natural sources. Set up collection surfaces (tarps, clean roofing) and storage. First flush (first few minutes of rain) may contain contaminants from the collection surface — divert it.
Atmospheric Water (Dew, Fog)
Low yield but useful in emergencies. Wrap clean cloth around ankles and walk through grass at dawn, then wring out. Fog nets can collect 5-15 liters/day in coastal areas.
Purification Methods
Boiling
99.99% Easy ▼
The gold standard. A rolling boil for 1 minute kills all bacteria, viruses, and protozoa. At altitudes above 2,000m, boil for 3 minutes (lower boiling point).
Pros: Kills everything biological, requires no special equipment. Cons: Requires fuel, doesn’t remove chemical contaminants, water must cool before drinking.
Chemical Treatment (Bleach/Chlorine)
99.9% Easy ▼
Add 2 drops of unscented household bleach (6-8.25% sodium hypochlorite) per liter. Stir and wait 30 minutes. Water should have slight chlorine smell — if not, repeat and wait 15 more minutes.
Pros: Lightweight, cheap, long shelf life, effective against bacteria and viruses. Cons: Less effective against Cryptosporidium, adds taste, requires correct dosing.
Filtration (Ceramic/Carbon)
99.9% bacteria Moderate ▼
Ceramic filters (like those in gravity-fed systems) physically remove bacteria and protozoa. Activated carbon also removes some chemicals and improves taste. Pore size matters: 0.2 micron removes bacteria, you need 0.02 micron for viruses.
Pros: No fuel needed, removes sediment, reusable. Cons: Doesn’t remove viruses (unless ultrafiltration), filters clog and need cleaning, can break.
Solar Disinfection (SODIS)
99.9% Easy ▼
Fill clear PET plastic bottles with water and place in direct sunlight for 6 hours (or 2 days if cloudy). UV radiation and heat kill pathogens.
Pros: Free, no equipment beyond bottles, proven by WHO. Cons: Slow, requires clear bottles and sunlight, small batch sizes, doesn’t remove chemicals.
UV Light (SteriPEN)
99.99% Easy ▼
Battery-powered UV light devices purify 1 liter in 90 seconds. Stir the light in the water for the indicated time.
Pros: Fast, effective against all biologicals, compact. Cons: Requires batteries/charging, doesn’t work in turbid water, no residual protection.
Method Comparison
| Method | Bacteria | Viruses | Protozoa | Chemicals | Speed | Fuel Needed |
|---|---|---|---|---|---|---|
| Boiling | ✅ | ✅ | ✅ | ❌ | 5-10 min | Yes |
| Bleach/Chlorine | ✅ | ✅ | ⚠️ | ❌ | 30 min | No |
| Ceramic Filter | ✅ | ❌ | ✅ | ⚠️ | Continuous | No |
| SODIS | ✅ | ✅ | ✅ | ❌ | 6+ hours | No |
| UV Light | ✅ | ✅ | ✅ | ❌ | 90 sec | Batteries |
| Distillation | ✅ | ✅ | ✅ | ✅ | Hours | Yes |
Myth Busted
Clear water is safe to drink
Many deadly pathogens are invisible. Crystal-clear mountain streams can contain Giardia from animal waste upstream. Always purify, no matter how clean it looks.
Myth Busted
You can drink urine in an emergency
Urine contains waste products your kidneys already filtered out. Drinking it accelerates dehydration. In extreme situations, it can be distilled (evaporated and recondensed) but never drunk directly.
Myth Busted
Adding bleach makes water dangerous
At proper doses (2 drops per liter), chlorine concentration is far below harmful levels — similar to municipal tap water. It’s been used safely for over a century.
🔬 How Boiling Actually Works Click to expand
Boiling doesn’t just “cook” pathogens. At 100°C, the heat denatures (unfolds) the proteins that bacteria and viruses need to function. Their cell membranes rupture, DNA breaks down, and enzymes stop working. Even heat-resistant cysts like Giardia are destroyed in under a minute at boiling temperature. The 1-minute recommendation includes a safety margin.
🔬 Why Filters Have Pore Size Ratings Click to expand
Microorganisms vary enormously in size. Protozoa (like Giardia) are 5-15 micrometers — easily caught by 0.2μm filters. Bacteria (like E. coli) are 0.2-5μm — caught by fine ceramic. But viruses (like Hepatitis A) are only 0.02-0.3μm — they slip right through standard filters. This is why combining filtration with chemical treatment or UV gives the best protection.