Quick Answer
A cistern is a viable backup water source for emergencies, providing a self-contained water storage system that can supply households with water during droughts, power outages, or other disruptions to municipal water supplies.
Understanding Cistern Sizing
When sizing a cistern, it’s essential to calculate the household’s water demand and then select a tank that can store enough water to meet that demand for at least 3-5 days. A general rule of thumb is to assume a household uses about 50-100 gallons of water per person per day. For a family of four, this translates to a cistern with a minimum capacity of 200-400 gallons.
Factors Affecting Cistern Capacity
Several factors affect cistern capacity, including rainwater collection area, roof size, and rainfall intensity. A larger roof area and higher rainfall rates require larger cisterns to capture and store the increased water volumes. For example, a 1,000 square foot roof with a rainfall rate of 0.5 inches per hour can collect up to 125 gallons of water per hour, suggesting a cistern with a minimum capacity of 5,000 gallons to support a family of four for a week.
Best Practices for Cistern Design
To ensure optimal cistern performance, it’s crucial to follow best practices in design and installation. These include using food-grade tanks, installing a first flush device to prevent debris and contaminants from entering the cistern, and incorporating a float valve to maintain the optimal water level. Additionally, cisterns should be located above the water table and protected from potential flood zones to prevent contamination. Regular maintenance and inspections are also essential to ensure the cistern remains safe and functional.
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