Filtration

There are varying levels of filtration which require different levels of power, ranging from “0” power, (gravity flow) to high power (osmotic flow), often times referred to as “reverse osmosis “.  Gravity types of filters vary from contained (vertical or horizontal tube type) with gravel, sand, and charcoal layers  to open types which can be natural fields though which small streams or subterranean flow feeds a natural or man made cistern (container). These fields are sometimes called (alluvial fans) when occurring in nature. 

Powered type filtration is usually required only when excessive amounts of virulent sewage or heavy metals are present.  When these conditions are present, the most effective means of filtration is reverse osmosis, which can require considerable electrical power because it would be like pressing water through multiple layers of your skin and getting a flow rate like the tap at your sink.