The key piece of the geothermal system is the ground loop. This is made of conventional polyethylene pipe, with thermally fused joints for reliability – most carry 50-year warranties! A fluid, often including a non-toxic antifreeze (propylene glycol), is pumped through this ground loop by a small circulating pump. It is this fluid that transfers the heat to/from the ground and your building. The heat pump unit is connected to the loop and operates as explained above. Heat pumps have become a common piece of mechanical equipment, and are made and sold by many of the heating and cooling companies that supply conventional equipment.