Gray water

Gray water is the wastewater that does not contain urine or fecal mater that is generated from structures such as households and offices. Sources of gray water include showers, bathtubs, sinks, washing machines, and dishwashers. It does not include wastewater from toilets, bidets, or urinals which is called black water. Gray water combined with black water is called sewage.

Gray water can be collected and lightly treated and used in toilets which do not need potable water. The reuse of gray water also reduces the amount of sewage septic systems or sewage treatment plants need to process.