What is Greywater?

Greywater includes water that comes from:

• Baths and showers
• Hand basins
• Laundry (washing clothes)

This water has already been used once in the home, but it can still be useful for watering plants when applied properly.

Greywater does not include:

• Toilet water (this is called blackwater)
• Water used to wash nappies
• Water that is heavily contaminated with fats, oils, or food waste

Blackwater must always go into a sewer or septic system and should never be reused for food production.

When greywater is applied directly to the soil:

• It moves into the root zone of plants
• The soil helps filter and break down contaminants
• Micro-organisms in healthy soil assist with natural purification

Because of this natural filtering process, greywater does not need chemical treatment before being used in gardens. However, it still needs to be used carefully and responsibly.

Greywater can contain:

• Soap and detergent residues
• Small food particles
• Oils and grease
• Micro-organisms

If greywater is misused, it can:

• Damage soil structure
• Harm plants
• Create health risks

For this reason, learning what greywater is and how it differs from other wastewater is the first important step before using it in food production.

Take a moment to think about your own household:

• Where does water leave your home after being used?
• Which of these water sources could be greywater?
• Which ones should never be reused?

You will explore why and how to use greywater safely in the next session.