Clean water is something that most first-world citizens take for granted. There are many areas in the world where clean water is a luxury. There are also many situations locally where clean water can be hard to come by. Filtering dirty water using something as simple as a coffee filter, however, can eliminate many obvious impurities.
Set up the basic filtration system. Collect the water that you need to be filtered into one large container. This can be any large container, but one with a pouring lip is the most user-friendly. Near the large container of dirty water, set up your series of bottles that you will be filtering the cleaner water into. Make sure that they are nearby, as the bucket of dirty water will most likely be very heavy and cumbersome. Make sure that the funnel you have can fit into each of the bottles' narrow mouths.
Insert the filter effectively. To create an effective filtration device from the coffee filter, flatten out one large drip coffee filter so that it is a large circle. Now, fold once in half twice so that it is a triangular shape. Open one of the inner triangle's flaps and fit the filter into the funnel. Dab the filter with a little water to make the filter stick to the funnel and conform to its shape.
Begin filtering the water. Once the filter is fitted securely into the funnel, and the funnel is inside the mouth of one of the empty bottles, begin pouring the dirty water very slowly into the funnel. The filter will begin catching all of the impurities that it can. These include dirt, silt, sand, pebbles and any other larger impurities that will not be able to pass through the coffee filter. Stop every few seconds to monitor the filtration. As you continue pouring, the filtration will get slower and slower, as the filter becomes more and more full of the dirt that is being filtered out of the water.
Once the filter is so full of dirt that clean water is no longer able to pass at a rapid rate, replace the coffee filter with a new one. Also, pay close attention to the level of water in each of the bottles. It is easy to forget about that, and let the clean water begin to overflow.
Store your clean water properly. Once you have filtered all of your dirty water into cleaner water, place caps on the tops of your water bottles and store in a refrigerator or a dark, cool place.