Question: Filter water using a charcoal filter.
Option 0: Instead of coffee grounds, use activated charcoal.  Rinse the charcoal well before placing the charcoal in a coffee filter.  Place the coffee filter into the coffee maker and proceed as if making coffee, instead it will be clean water.
Option 1: Place active charcoal in a pitcher.  Fill the pitcher with water to be filtered.  Place the pitcher int he sun and wait.  After a few hours the water will be pure.
Answer: 0