1️⃣Materials needed:
Plastic bottle cut in half (top half = funnel, bottom half = container),
stones or gravel
, coarse sand , fine
sand ,
coffee filter or clean cloth
, rubber band .
2️⃣Assembling the filter
: Turn the top half of the bottle upside down and secure the coffee filter to the neck of the bottle with a rubber band.
Fill the bottle with the following layers from top to bottom: stones, coarse sand, fine sand.
Place the funnel on the bottom half of the bottle.

3️⃣Instructions:
Slowly pour the cloudy water into the funnel.

The water permeates the layers and flows more clearly into the container below.

4️⃣How it works:
Stones → filter out coarse particles and dirt.
Coarse sand → filters out medium particles.
Fine sand → filters out fine particles.

Coffee filter → last barrier against remaining impurities.

5️⃣Important warnings
: This system clarifies the water, but does not make it safe to drink. It does not remove bacteria, viruses, or chemicals. Before drinking, the water must be boiled for at least 1 minute (3 minutes at high altitudes) or disinfected with disinfectant tablets, chlorine, or certified filters.
While a simple and educational method, useful for excursions or emergencies, it should always be supplemented by safe water purification procedures.