I have now had Central Boilers Thermopex in the ground for 7 years. Buried with only 6 inches of dirt over the top, where the ground freezes 4-5 feet deep in Central MN. Zero heat loss and Zero melting over the line. 90 feet from boiler to my house. You can't beat a urethane delivery line. Yeah, it costs a little more and is kind of a bear to handle, but once you have it in the trench, you won't have to deal with it again. Well worth the cost IMO.