Water used in homes i.e. residential waste water can be recycled and reused for other activities. This used water is known as Gray water and is sourced from water used in sinks, bathtubs, laundry, and dishwashers. Waste water from toilets also known as black water is not included as a source since it contains high levels of nitrogen and pathogens and does not decompose easily. It is advisable not to include water that was used to clean meat or poultry products and water that may be contaminated due to infectious diseases in the gray water recycle system.