Quick Answer
The general recommendation for larger properties is to have at least 2-5 cisterns, each holding 2,000 to 5,000 gallons of water, depending on the specific needs and climate of the area.
Determining Water Needs
When determining the number of cisterns needed for a larger property, consider the water needs of the household, livestock, and any irrigation requirements. A good rule of thumb is to calculate 1-2 gallons per minute for household use, and 1-5 gallons per minute for irrigation. For a 5-acre property, this could translate to 2,400 to 12,000 gallons of water per day. With a 2,000-gallon cistern, this would mean 2-6 cisterns, assuming a moderate usage rate.
Cistern Size and Storage Capacity
While 2,000 to 5,000 gallons per cistern is a good starting point, it’s essential to consider the specific needs of the property. For example, if there are multiple households or a large orchard, more cisterns with larger capacity may be necessary. On the other hand, smaller properties with low usage rates may require fewer but larger cisterns. Consider the following general guidelines for cistern size: 2,000 gallons for 1-2 households, 3,000 gallons for 2-4 households, and 5,000 gallons for 4-6 households.
Harvesting Rainwater and Greywater
In addition to cistern size, consider harvesting rainwater and greywater to supplement your water supply. This can help reduce the load on the cisterns and minimize wastewater. A general rule of thumb for rainwater harvesting is to collect 1 inch of rainfall per 1,000 square feet of roof area. For a 5-acre property, this could translate to 25,000 gallons of rainwater per inch of rainfall. Greywater systems can also provide an additional 10-20% of the household’s water needs.
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