system setup:Rainwater harvesting systems can be installed with minimal skills. The system should be sized to meet the water demand throughout the dry season since it must be big enough to support daily water consumption. Specifically, the rainfall capturing area such as a building roof must be large enough to maintain adequate flow. The water storage tank size should be large enough to contain the captured wate. 
this is a developed country(USA) where every thing is machine work,and some thing very little work is dun by human(man) so i thing that there are a little ahead of us, but we will do it....    

Rainwater harvesting(RWH) is a practice of growing importance in abroad, particularly in the South East of England where there is less water available per person than in many Mediterranean countries. Rainwater harvesting in abroad likein UK is both a traditional and reviving technique for collecting water for domestic uses This water is generally used for non-hygienic purposes like watering gardens, flushing toilets, and washing clothes. There is a growing demand for larger tank systems collecting between 1000-7500 litres of water. The two main uses for harvested rainwater are botanical uses, like gardening for plant irrigation, and domestic uses, like flushing toilets and running washing machine. Rainwater is almost always collected strictly from the roof, then heavily filtered using either a filter attached to the down pipe, a fine basket filter or for more expensive systems like self-cleaning filters placed in an underground tank. UK homes using some form of rainwater harvesting system can reduce their mains water usage by 50% or more.