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THEY CATCH WATER FROM THE SKY
Earthships have a water harvesting system that collects rain water and melted snow for household consumption. The figure to the right illustrates how a roof can be designed to harvest the rainwater and snowmelt. The roof has a six degree slope for the water to be collected in cisterns that are buried behind the building.
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S I LT F I LT E R
The water that is collected on the roof must be cleared of twigs, leaves, grass, dirt and other debris before it enters the cistern. To do this, a silt-filter is used to keep larger particles out. In a wet climate the silt-filter is designed to cope with heavy rainfall so that no water is lost.
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W AT E R C I S T E R N S The tanks used to store water in an Earthship are made out of hard plastic. For a household of four people anywhere from two to four tanks with a capacity of 5000 - 6000 liters each will normally work. Where there is heavy rainfall the tanks are often refilled and can therefore be smaller. In dry climates the tanks should be able to store a total of approximately 23 000 liters of water, while in wet climates a capacity of 11 000 liters or less is sufficient.
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W O M – W AT E R O R G A N I Z I N G M O D U L E WOM is a specially designed filtering device for filtering water to the household. After the rain water has been treated by WOM, it is clean enough to be used for domestic purposes. WOM is a prefabricated unit that is connected to the cisterns. The water passes through four different filters and delivers clean drinking water.
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