How to Collect and use Greywater in the Garden

Greywater is water that comes from household washing machines, hand basins, showers and baths. Water from dishwashers and kitchen sinks is often referred to as ‘dark greywater' as it has a higher load of chemicals, fats and other organic matter. Dark greywater is not recommended for using on gardens. Water from toilets is called  ‘blackwater' and is also not safe to use on gardens. 

Consult your local council or water authority for the latest regulations regarding greywater usage in your area. In some areas, untreated greywater can only be used in sub-surface irrigation systems.

However, here is some general information on using greywater in your garden.

When used correctly, greywater has the potential to irrigate lawns and gardens. This helps keep gardens thriving and makes the most of precious water resources, particularly during times of drought and water restrictions. Using greywater also helps to reduce water bills and the amount of wastewater entering sewers or on-site treatment systems.

When diverting greywater directly from the laundry, it's best to regularly move greywater hoses around the garden and lawn so the same plants / areas are not being constantly watered with greywater. A handy way to remember is to move greywater hoses from one spot to another every weekend.

It's important to choose laundry detergents that are suitable for using in greywater. Detergents can contain phosphorus and salts that can harm some plants and affect the quality of the soil or increase the soil's pH (make the soil more alkaline). Soil with an alkaline pH (pH greater than 7) can lead to nutrients becoming unavailable to plants, particularly iron. You may start to see plant leaves becoming pale with dark green veins, which indicates an iron deficiency. High concentrations of salts can also damage plants and lead to burnt leaves and poor plant health. If plants irrigated with greywater start to develop pale or discoloured leaves, discontinue using greywater in that area.

Look on detergent labels for information about whether it's suitable for greywater usage. Product labels may say ‘Greywater safe' or ‘Greywater friendly'. Some laundry detergent manufacturers recommend only using washing machine rinse water to irrigate the garden and not the wash cycle water, so this needs to be taken in account when using greywater.

Lanfax Labs provides information on the suitability of some detergents when using greywater.

Yates Greywater Fertiliser to greywater to help minimise the negative effects of soaps and detergents on soil quality.

• Adds missing plant nutrients to greywater. Added nitrogen and chelated iron to promote green leaf growth and potassium to encourage healthy plants and flowering.
• Helps neutralise the effect of alkaline soaps and detergents on soil pH.
• Contains a biocide to help kill unwanted microbes in greywater.
• Added calcium to reduce the potential negative effects on soil quality from prolonged greywater use.

Mix 20–40 mL of Yates Greywater Fertiliser into 10 L of greywater and apply around the root zone of non-edible garden plants or over the lawn every 2–4 weeks.

• Don't store greywater for more than 24 hours, as it can become a source of infection and can start to smell.
• Keep buckets and tubs of greywater away from babies and children.
• Do not use greywater when family members are ill with a gastrointestinal infection or from the washing machine when washing dirty nappies. It's best to avoid contact with greywater and not allow people or pets to walk or play in areas that are being irrigated with greywater. Leave the area to dry for at least 24 hours before allowing people and pets back onto the area. This helps reduce any contact with potential sources of bacteria and infection that may be in the greywater.