Water Filtering Step by Step: From Puddle to Drinking Water

Foreword: What You Should NEVER Drink Without Treatment

No water source is safe without treatment — except sealed bottled water or your own filled, known-clean water.

Never drink untreated:

• River water, lake water, pond water
• Rainwater (contains air pollutants and microorganisms)
• Well water of unknown origin
• Tap water after a pipe break or flooding

Step 1: Find a Suitable Water Source

Not all water sources are equal — start with the cleanest one you can find.

Sources by preference (best first):

1. Mountain spring water (flowing from a rocky spring): Often very clean, usually only biological treatment needed
2. Flowing river water (upstream, far from settlements): Good, but biological and chemical contamination possible
3. Pond water, standing water: Higher biological risk, often turbid
4. Rainwater (collected in a clean container): Relatively clean biologically, but air pollutants present
5. Water near urban areas, farmland: Very high chemical contamination risk

Warning signs of heavily contaminated water:

• Unusual color (red, blue, green, very turbid)
• Strong odor (chemicals, sulfur, putrefaction)
• Dead vegetation or fish nearby
• Industrial area, agriculture immediately at the bank

Step 2: Coarse Pre-Filtering (Always)

Regardless of your main filtration method: always remove coarse particles first.

Method A — Cloth/T-shirt:

1. Take a clean, tightly woven cloth (cotton, multiple layers)
2. Stretch it over a container
3. Slowly pour water through
4. Repeat with a second, finer cloth

Method B — Coffee filter/paper: A coffee filter removes very fine particles but is less robust than fabric.

Method C — Gravity settling: Fill a container, let stand 30-60 minutes. Sediment settles. Carefully scoop the top 2/3 of the water into a new container.

Step 3: Main Filtration Based on Available Equipment

Option A: Professional Water Filter (Sawyer, Katadyn, LifeStraw)

1. Fill input bag/container with pre-filtered water
2. Attach filter
3. Let water run through (Sawyer: pressure from bag; LifeStraw: suction)
4. Collect filtered water in a clean container
5. After 1-2 liters: backflush (included syringe) to restore capacity

Result: Free from bacteria and protozoa (treat viruses separately if needed)

Option B: Build an Improvised Gravity Filter

If no professional filter is available:

Materials:

• 2 plastic bottles (1.5-2 liters)
• Fine sand (clean, from a stream or dune sand)
• Coarse sand or small stones
• Activated charcoal (from burned, cleaned wood, or from aquarium use)
• Fine-woven cloth or coffee filter

Construction:

1. Cut the bottom off one bottle, flip it upside down (opening facing down)
2. Layer from bottom to top: fine cloth → fine sand (~10 cm) → activated charcoal (~5 cm) → coarse sand (~10 cm) → rough stones (~5 cm)
3. Place this bottle on top of the second bottle (as collection container)
4. Pour pre-filtered water slowly from the top through

Important: This DIY filter removes sediments and improves taste, but is NOT a safety filter against bacteria or viruses. Always subsequently boil or chemically treat.

Step 4: Disinfection (Always with Unknown Sources)

After filtering: always disinfect.

Method A: Boiling

1. Bring filtered water to a boil in a clean pot
2. Maintain at full rolling boil for at least 1 minute
3. At altitudes above 2,000 m: boil 3 minutes
4. Let cool (in clean, closed container)

Method B: Chlorine Tablets (Micropur Forte, Aquatabs)

1. Filter water (must be clear for full effectiveness)
2. 1 tablet per liter of clear water
3. Stir well
4. Wait 30 minutes before drinking (cold water: 60 minutes)

Method C: UV Pen (SteriPen)

1. Water MUST be clear (pre-filter!)
2. Turn on device, hold in water
3. Stir/swirl for indicated time (usually 60-90 seconds per liter)

Step 5: Optional — Improve Taste

After disinfection, water may taste of chlorine or be "flat."

• Add activated carbon pouch: For 15-30 minutes, improves taste
• Aerate: Let boiled water stand open for 30 minutes (chlorine dissipates)
• Transfer: Pour between two containers several times to add oxygen

Safety Checklist After Treatment

Before drinking:

• Water was pre-filtered
• Biologically disinfected (boiled, chlorine, or UV)
• Collected in clean container (no contact with untreated water)
• Container sealed with lid
• Not stored more than 24 hours (then re-treat or filter)