It is a storage tank usually fitted underground to your down pipes coming from the roof. Rainwater enters the tank through a filter which removes the leaves and other debris. The system contains a pump which pushes or sucks the rain water back into the house where it is delivered to the toilets or clothes washing machine. The tank is placed in the dark and kept oxygenated to prevent the growth of algae. This filtered untreated water should not be used for drinking. Rain water harvesters can be installed in houses, bungalows, large sheds or any building with a roof on it to capture the rain water. Commercial premises are very suitable as they often have a larger roof space and higher percentage of water use that can be replaced by rain water.