Open Loop Heat Pump
An open loop, ground-water heat pump, uses a surface or underground water source (such as a lake, river, or well) as the heat source and sink. Well water designs are the most common and seem to be the most cost effective. The well supplies both domestic water and water for the heat pump.
Approximately three gallons per minute of well-water are needed per ton of cooling capacity. A 3,000 square foot, well-insulated home would typically require 10 to 15 gallons per minute.