Pipes from the water source to the heat pump should be buried below the frost line to prevent freezing. The pipes must be able to accommodate a minimum flow of three gallons per minute per 12,000 Btuh of cooling capacity. Pump and pipe sizing are very important factors in a water-source heat pump and should be done by a qualified professional. Pumps must supply the maximum flow rate required by the heat pump and provide enough pressure to overcome friction losses in the pipe and heat pump. Sealed pipe loops are placed in the ground to serve as the heat exchanger.
Water is circulated inside the loop and carries heat between the ground and the heat pump.
Normally, the loops are filled with water and a corrosion inhibitor to slow the deterioration of metal components. The hole requires no casing and is normally backfilled with sand or gravel and earth from the drilling. Several U-shaped sections can be connected to provide enough heat exchange capacity. One such hole is good for about one ton of cooling capacity. Horizontal pipe loops demand more land than vertical loops.