Dear roberben, The installation with hot melt pipes in direct contact with the earth does not have disadvantages, except that your installation is in VERY cold or very earthy places. You should only observe that if you are in a VERY COLD region (such as Patagonia where there are temperatures below zero) you should insulate the pipes. I have seen facilities in Neuquén where people went on winter vacations for 2 weeks and the water, inside the pipes, froze. When they returned from vacation, they had no water but having [...] good hot melt pipes [/i], they did not break, because the material and its joints expand and contract; something that does not happen with the threaded or glued systems of more rigid plastics. I hope you find it useful.