Quick Answer
To build a cistern for rainwater collection, dig a hole with a concrete liner and a waterproof coating, then attach a roof collection system. Size the cistern based on the roof area and desired storage capacity. Ensure proper overflow and drainage.
Cistern Design and Construction
When building a cistern, choose a location that is level, well-drained, and partially shaded. The ideal size of the cistern depends on the roof area and the desired storage capacity. A general rule of thumb is to size the cistern to hold 1,000 to 1,500 gallons of water per 1,000 square feet of roof area. For a typical residential roof of 2,000 square feet, a 2,000 to 3,000 gallon cistern would be sufficient.
Liner and Waterproofing
To prevent leaks and contamination, line the cistern with a durable, food-grade liner. A 20-mil or thicker liner is recommended for a cistern that will hold potable water. Apply a waterproof coating to the liner, such as a polyurethane-based sealant, to prevent leaks and ensure the integrity of the liner.
Roof Collection System
Design a roof collection system that directs rainwater from the roof into the cistern. Use a series of downspouts and gutters to collect and channel the water into a network of pipes that lead to the cistern. Ensure the collection system is sloped to prevent water from pooling on the roof and to direct it towards the cistern.
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