Grey water is made up of bath, shower, hand basin and washing machine water. Kitchen water is also Grey-water, but not advisable because of grease, plant and animal fats. Not only are these pathogen-generating, but they form a layer just below the surface that stops aeration and moisture penetration. This essentially suffocates the plants.

An average household (family of 4) will use between 2000 and 3000 litres of reusable water on a daily basis. The shampoos, soaps and body hygiene products saturated in the water can provide useful sulphates, nitrates, nutrients and minerals which most experts say is more beneficial to the garden than clean tap water or chlorine-treated water.

It is advisable to use biodegradable products in the washing machine. The average suburban garden accounts for about 35% of domestic water consumption. Most of the concerns about grey-water are to do with hygiene and odours of the water, but both these aspects are eliminated if the water is re-used as soon as possible and bacteria has not been given the chance to reproduce.