A pond loop is another closed ground loop for a geothermal system, except instead of trenching or drilling holes, large coils of tubing is submerged in a local body of water, like a pond or a lake. This makes the water of the pond the heat exchanger of the system.

This method is a great option if there is a sufficiently sized pond close to the structure, because there is very little trenching and excavation needed. Because of that it can be very cost effective to install this system over another type.

The size of the loops on this ground loop will need to take into account more things than the standard earth ground loop.