Grey water is household or office waste water generated from activities such as laundry, dishwashing, 
bathing, and washing foods. Grey water does not include water that has come into contact with feces, which is referred to as black water. Grey water contains fewer pathogens than black water and has many potential uses, such as landscape irrigation. However, caution must be taken, as grey water does pose health risks if it is ingested. Link to Health Canada for more information.
As long as precautions are taken to ensure that grey water will not be accidentally consumed, using it for non-potable purposes is a way to cut down on personal water consumption.