Interactive lesson

Greywater, step by step

Interactive lesson: which water from the house may go on the garden and which never, a laundry-to-landscape system, the mulch basin, the septic tank and the dry toilet.

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The whole lesson as text

1. Which water goes where

A family of four sends 200–300 litres (50–80 US gallons) of water down the drain every day from showers, hand basins and laundry.

Greywater from the bathroom — Shower, bath and hand basin give roughly 40–55 L per person per day. That water goes on the garden, under mulch.
Water from the washing machine — The washing machine gives 15–20 L per person per day. It also goes on the garden under mulch, with the right products.
Kitchen water to the septic tank — Kitchen water carries fat, food scraps and more germs. Beginners send it to the septic tank or the sewer.
Toilet water never on the garden — Blackwater from the toilet goes to the septic tank or the sewer, or you use a dry toilet. Zero litres of toilet water on the garden.

Why: That is almost what a 60 m² (650 sq ft) garden needs in August. But not all the water from the house is the same: some may go on the garden, some never. Separate them first.

Don't store greywater for more than 24 hours: in a barrel it turns smelly and full of germs within a day.
Fat into a jar, not down the sink. A strainer in the sink and a grease trap save both the pipes and the septic tank.

2. What may go on the garden

Greywater goes under mulch, into the soil, and only under plants where you don't eat the part that touches the ground.

Fruit trees drink best — Apple, plum, walnut and hazel have deep roots, and the fruit is well clear of the ground.
Soft fruit and vines — Raspberry, currants, aronia and grapevine get their water in a mulch basin beside the bush, never on the fruit.
Never on lettuce — Not on lettuce, radish or strawberries, nor on carrots, potatoes or onions. And never by spraying.
Rotate and keep your distance — Three to five basins in turn. Roughly 30 m (100 ft) from wells and springs, at least 2–3 m (7–10 ft) from the house foundations.

Why: Greywater contains germs from the human body, even when it looks clean. So you don't spray it and you don't run it over vegetables. Fruit trees, shrubs and flowers are happy to drink it.

Greywater is slightly alkaline: keep it away from blueberries and other acid-loving plants.
Don't let it run into a stream, a ditch or onto the neighbour's land. Wash your hands after working on the system.