Quick Answer
A recommended size for cisterns off-grid homes varies depending on household size, climate, and water usage, but a general guideline is 1,000 to 2,000 gallons for a small to medium-sized household.
Calculating Cistern Capacity
When determining the size of a cistern for an off-grid home, it’s essential to consider the household’s water usage. A general rule of thumb is to calculate the daily water usage in gallons and multiply it by 365 (days in a year). For example, if the household uses 20 gallons per day, a 7,300-gallon cistern (20 gallons/day x 365 days) could provide approximately 2-3 months of water storage.
Cistern Materials and Design
A buried concrete cistern is a popular choice for off-grid homes due to its durability and low maintenance. The American Society of Civil Engineers (ASCE) recommends a minimum thickness of 6 inches (152 mm) for a concrete cistern, and a maximum height of 6 feet (1.83 meters) to prevent collapse under soil pressure. It’s also essential to consider the cistern’s material and design to prevent leaks and contamination.
Additional Considerations
In addition to calculating the cistern’s capacity and selecting suitable materials, it’s crucial to consider other factors, such as the cistern’s location, drainage system, and access for maintenance. The cistern should be located away from potential sources of contamination, such as septic systems or animal enclosures. A shallow well or sump pump may be necessary to drain the cistern when it reaches capacity.
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