We have enjoyed our pump-and-dump geothermal system for 25 years. Due to the poor water quality and likely build up of rust partially occluded the plumbing, we are opting for a new closed-loop system at this time. We have received estimates from a DX installer and a traditional polyethylene installer. Both are reputable installers in our area. The DX system is estimated to cost approximately $10,000 more than the traditional system apparently due to the cost of copper. The DX installer claims that the cost to heat and cool the house will be much more efficient than polyethylene . My question is if the premium price to install would be worth the future cost savings? In addition, I have read about copper corrosion and subsequent freon leaks. The DX installer claims that they have a special anode that monitors the pressures in the copper pipes. Any experiences or recommendations about copper versus polyethylene would be appreciated as much of the information I have read on this is greater than five years old; I am not sure if this remains a problem for the DX system.