Grey water is wastewater produced within buildings which does not have human or animal waste/contamination. Wastewater from sinks, showers, washing machines, dishwashers and machine washdown are the most common sources of greywater. Toilet water is not considered to be greywater.
70-80% of all wastewater created in an average building can be greywater. Greywater will contain traces of food, dirt, grease and cleaning products and should never be considered for drinking, but can be used to supplement non-potable water sources. Greywater should be treated prior to use, with its end use determining the level of treatment required. Ideally, grey water should be treated immediately before storage to prevent fouling of water. The required treatment level will depend on the quality of greywater, but will likely include physical filtration, reedbed/biological treatment and UV sterilisation. Any stored untreated greywater should be constantly recirculated to prevent issues developing with the water