Water Purification Methods

What's Your Situation?

• Clear water, no chemicals suspected: Filter OR boil OR chemical
• Cloudy water: Pre-filter (cloth/sand) → then boil OR chemical + filter
• Chemical contamination suspected (agricultural, industrial): Activated carbon filter + distillation if possible
• Viral risk (area with known outbreaks): Boil OR chemical (filters don't catch viruses well)
• Maximum safety: Pre-filter → Boil → Chemical → Filter (overkill but certain)

How It Works

Heat kills pathogens. Simple, reliable, no special equipment needed beyond heat source and container.

Procedure

1. If cloudy, let settle or filter through cloth first
2. Bring water to rolling boil
3. Maintain boil for 1 minute (3 minutes above 6500 ft elevation)
4. Let cool before drinking
5. Store in clean, covered container

Boiled water tastes flat. Pour between containers to add oxygen back, or add pinch of salt.

Pros & Cons

How It Works

Physical barrier removes particles and pathogens. Pore size determines what gets filtered.

• 0.1 micron: Bacteria, protozoa, sediment
• 0.02 micron: Most viruses
• Activated carbon: Chemicals, bad taste, odor

Filter Types

Sawyer squeeze filters have the best value - 100,000 gallon rating for ~$40.

Pros & Cons

DIY Filter (Emergency)

1. Cut bottom off plastic bottle
2. Layer from bottom up: cotton cloth, activated charcoal, fine sand, coarse sand, small gravel
3. Pour water through, collect from bottle cap
4. Still need to boil or chemically treat after!

DIY filters are for pre-filtering sediment only. They do NOT make water safe to drink. Must combine with boiling or chemical treatment.

Chlorine Dioxide (Tablets/Drops)

Kills bacteria, viruses, some protozoa. Most practical chemical option.

• Brands: Potable Aqua, Aquatabs, Aquamira
• Dose: Follow package (typically 1-2 tablets per liter)
• Wait time: 30 minutes (4 hours for crypto)
• Shelf life: 4-5 years sealed

Aquatabs are cheap and effective. 100 tablets for ~$10. One tablet treats 1 liter.

Household Bleach (Unscented)

Emergency backup using regular bleach. Not ideal but works.

• Bleach type: Unscented, no additives, 5-6% sodium hypochlorite
• Dose: 2 drops per liter (8 per gallon) for clear water
• Dose: 4 drops per liter (16 per gallon) for cloudy water
• Wait time: 30 minutes

Don't use scented bleach, color-safe bleach, or bleach with additives. Check expiration - bleach loses potency over time.

Iodine (Tablets/Crystals)

Older method, still works but has limitations.

• Pros: Long shelf life, lightweight
• Cons: Bad taste, not effective against crypto, health concerns with long-term use
• Not for: Pregnant women, thyroid conditions, extended use

Iodine is being replaced by chlorine dioxide. Still in many kits but not recommended as primary method.

How It Works

UV light damages pathogen DNA, preventing reproduction. Effective against bacteria, viruses, protozoa.

Devices

• SteriPEN: Battery-powered UV wand. Insert in water, activate, wait 60-90 seconds.
• Solar disinfection (SODIS): Leave clear plastic bottles in direct sunlight for 6+ hours.

SteriPEN is fast and effective but needs batteries and clear water. Keep as backup, not primary.

Pros & Cons

How It Works

Boil water, collect the steam, condense back to liquid. Leaves behind virtually all contaminants including salt, heavy metals, and most chemicals.

Simple Setup

1. Boil water in large pot
2. Place smaller collection bowl in center (floating or on rack)
3. Invert pot lid, cover with cold water or ice
4. Steam condenses on lid, drips into collection bowl
5. Collect distilled water from bowl

Distillation is slow and fuel-intensive. Use when chemical contamination is a concern or for desalination.

Recommended Combinations

• Clear backcountry water: Filter alone is fine
• Questionable source: Pre-filter → Chemical → Filter
• Viral risk area: Pre-filter → Chemical (or boil)
• Chemical concern: Carbon filter → Distill if serious
• Maximum certainty: Pre-filter → Boil → Chemical

Filter clogged with sediment

1. Pre-filter next batch through cloth or let settle
2. Backflush filter if applicable (Sawyer)
3. If still clogged, switch to chemical treatment
4. Boil as backup if fuel available

Chemical tablets expired

1. May still work - potency decreases but doesn't vanish
2. Increase wait time (double it)
3. Boil if possible for certainty
4. Replace with fresh tablets when available

Water smells like chemicals/fuel

1. Don't drink if possible - find another source
2. If no alternative: activated carbon filter first
3. Then distill if equipment available
4. Boiling doesn't remove chemicals - concentrates them