Quick Answer
Cistern roof catchment systems collect and store rainwater from a roof for non-potable uses, such as irrigation and toilet flushing. The system consists of a roof catchment area, gutter system, and storage tank. Proper sizing and maintenance are crucial for safe and efficient water collection.
Roof Catchment Area Design
A roof catchment area should be designed to maximize rainfall collection while minimizing contaminants. A general rule of thumb is to use a roof catchment area that is at least 2,000 square feet to supply 1,000 gallons of water storage. The catchment area should be free of debris, leaves, and other contaminants that can enter the storage tank.
Cistern Sizing Calculations
Cistern sizing is critical to ensure adequate water storage for household needs. A general rule of thumb is to size the cistern to store at least 1,000 gallons of water for every 2,000 square feet of roof catchment area. For example, a 3,000 square foot roof catchment area would require a 1,500 gallon cistern. It’s also essential to consider factors such as household water usage, irrigation needs, and rainfall patterns when determining cistern size.
Maintenance and First Flush Devices
Regular maintenance is crucial to prevent contamination of the stored water. A first flush device is often installed at the top of the gutter system to divert the first flow of water from the roof, which can contain contaminants, into the storm drain, and then allow clean water to flow into the storage tank. Regular cleaning and inspection of the system, including the roof catchment area, gutters, and storage tank, are also essential to ensure safe and efficient water collection.
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