Lake or pond loops are very economical closed loop systems. The key to this process is that the lake or pond must remain at a minimum of 8 feet deep. The process entails sinking the loop into the water and using the water for our heat transfer. Water is always the better heat transfer.
Economical heat exchange Very good heat transfer Little to no maintenance
Silt could cover loop, destroying heat transfer
The photo above depicts a pond loop being installed.