Greywater Recycling Overview
Grey water represents up to 70% of wastewater output resulting from showers, baths and taps and thus a potentially great resource.
Historically greywater has been the poor relation of water recycling owing to the difficulties of treating greywater. With the presence of organic matter, bacteria, detergents the treatment has been complex, large and expensive and so not suitable for a domestic set up. Thus rainwater harvesting (recycling) is usually the initial consideration due to its comparable simplicity.
Modern systems now allow greywater to be recycled and reused in packaged systems. The cost benefit is not as high as a rainwater system but does benefit from being typically a smaller system housed indoors and not requiring a an underground tank.
For more information on greywater systems see here.