It is important to draw a distinction between blackwater and greywater when looking at installing a home water treatment system. Water that has been mixed with the waste from the toilet and requires biological or chemical treatment before it can be re-used is classified as backwater and is only suitable for outdoor use. Greywater is water that comes from plumbing fixtures other than the toilet (showers, basins, taps). Greywater can be re-used indoors for toilet flushing and clothes washing and can also be used for watering the garden.