As water rates increasingly reflect the fact that water is a limited resource to be treated with greater respect, a rainwater collection system has become equally more viable. Rainwater is perfect for those situations where using expensive and limited drinking water is not just unnecessary, but even inappropriate seen from an environmental point of view. Rainwater Harvesting is a technology used for collecting and storing rainwater from rooftops or underground by using simple techniques. These techniques usually serve as major sources of saving precious drinking water from toilet and garden applications at home or even flushing systems in commercial buildings. Rainwater Harvesting is a technology used for collecting and storing rainwater from rooftops or underground by using simple techniques. These techniques usually serve as major sources of saving precious drinking water from toilet and garden applications at home or even flushing systems in commercial buildings. The rainwater harvesting methodology which is ecofriendly when it is implemented will enable owners to enjoy great savings on water utility bill. As it collects rainwater from its environment and natural resources it even reduces flooding area where drainage is bad. In major cities, rainwater harvesting has become mandatory for all new housing and commercial developments. In Kathmandu and major cities of Nepal, rainwater harvesting system is part of the criteria for approval for all new constructions, as well as renovation works of more than 70% for old homes.