Not sure if it is safe to use PVC for drinking water leaches chlorine I believe. Plastics will last best under ground, no UV. Any plastic could have unknown health implications, copper is known to be poisonous, read some where when opening a tap brass (copper zinc alloy)is worn from the seat and will end up in that glass of water you are just about to swallow. That is beside the fluoride and chlorine etc of coarse. Aluminium is used for high power transition lines but has a steel core to make it strong enough to span long distances without breaking. I think weight for weight it is a better conductor than copper, but size for size is not, The better welders use copper transformers rather than aluminium. Ideally my water would come through Silver pipes! Silver is the best conductor of electricity better than gold I believe. Quite a large amount of Silver is used in ICBM`s Silver solder is quite strong and easy to do. Great for joining copper or brass steel etc. Heaps of uses for silver. Maybe its best IMO is its reflectivity in conjunction with solar. All off the top of my head and don`t mind being corrected.
