We need to replace the 60 year old water pipes leading from the overhead water storage tank to the ranch house pressure pump, approximately 150' length. We have gophers. We also have hard water. The existing line is buried 20" deep and, even in the coldest winters, has not had a problem with freezing. Over the course of a few years, we have been replacing the inside water pipes with PVC and PEX. What would be the best material to replace the outside supply lines with? Galvanized corrodes, which is what we are having issues with now; PEX is plastic and I have heard, is a magnet for rodents, such as gophers. Copper also corrodes. All work will need to be done by us, as the nearest plumber is more than 80 miles away and won't come out. Being ranchers, we are proficient in completing renovations such as this.