This loop is composed of pipes that run horizontally in the ground. A long trench being dug which is deeper than the frost line, where dug and U shaped coils are placed horizontally inside the same trench. A trench which is made for horizontal loop is similar to slinky loop field. The width of loop strictly depends on the how many loops installed. Horizontal loop fields are very common. Horizontal loop are economical if there is adequate land available.

The horizontal system circulates water through a closed loop coil of high density polybutylene pipe buried horizontally. It is being installed according to climate, soil density and moisture conditions. In South Dakota, there pipes should be buried at depth about six feet. It is necessary; approximately 500 feet of underground pipe are required for each ton of heating and cooling capacity. As once the loop has been filled, then no additional water is required. Here another version of the closed loop system is called the slinky which uses coiled pipe in a trench.

The horizontal closed loop system is comprised of loops of pipes which are laid down 6 to 10 feet underground in trenches 2 to 4 feet apart. Horizontal Loop system normally used smaller buildings, it requires one acre of loop field per 24 tons of load.

For large, cooling dominated commercial building, rising of loop field temperature is kind of concern in the summer but not necessarily a problem. What happen peak loop field temperature used to lag about two months behind peak atmospheric temperature. So on these unusual warm late days, the temperature of return water can be 90 degrees. If the air temperature is 95 degrees properly designed systems can bring supply air temperature to 65 degrees. The cost for horizontal system can vary from $800 to $1,500 per ton.