When discussing a home water treatment system it is important to draw a distinction between blackwater and greywater. Blackwater is water that has been mixed with the waste from the toilet and requires biological or chemical treatment before it can be re-used. Blackwater 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.