Harvesting rainwater is generally the easiest way ensuring a clean water supply. Rainwater is usually very clean, and, unlike well water or mains water, there is no need to use energy to pump it long distances. Mike Reynolods, the inventor of Earthships, has said that a house with water-efficient fittings such as a greywater system can be self-sufficient using just rain water provided the annual rainfall is over 8 inches (20cm).
There are a number of options for filtering rainwater before use.
- http://www.climate-charts.com/World-Climate-Maps.html#rain World Map Annual Rainfall
- http://www.harvesth2o.com/ - The Online Rainwater Harvesting Community
- appropedia: Portal:Rainwater harvesting