If you ever carry a bowl of bathwater outside to water the plants then you are already recycling some of your greywater. Greywater is the used water from baths, showers and hand basins. It can be relatively clean – depending on how much soap, shampoo and shower gel you use – and it can be collected and reused.
Rainwater harvesting is the practice of collecting and using rainwater from hard surfaces such as roofs for applications like landscape irrigation or toilet flushing. Rainwater harvesting systems can be as simple as using a small home-made rain barrel or installing a large underground cistern or storage tank.