Copper piping has been popular in plumbing for many years, mostly as it is soft enough to bend easily, and can be joined using simple techniques. It is also a good conductor of electricity, making it useful for electrical grounding. It is thought not to pollute or react with water, though this matter is not certain.
One water hygiene advantage of copper pipe cladding is that it is bacteriostatic; bacteria will not grow in copper piping as it sometimes can in PVC. It is also fairly unreactive with clean water. But if the water is acidic or alkaline (base) it can cause copper corrosion. As we should not be drinking unclean water this should not be an issue.
There has concern over the past generation over chemicals leaching out of pipe cladding material such as plastics and PVC. The area is difficult to study as the variation between plastics is quite large, so it is hard to pin down any individual chemical problem. Plastics are common in the environment, and it is hard to see which plastics and which seeping chemicals are at fault. It is also hard to see if the problems only occur under certain circumstances. One solution is to not use PVC pipe cladding material for drinking water.
Copper pipe cladding material should not add anything to the water other than trace amounts of copper. The human body needs a very small amount of copper to stay healthy, and can deal with moderately larger doses in drinking water, but high doses of copper can be harmful. As long as the water is neither acidic nor hot the amount of copper coming from pipes is extremely low.
To avoid ingesting copper water should only be drunk from the cold tap; the hot water lines do pick up slightly more material from the pipe. Likewise, acidic food should not be cooked in copper utensils.
Copper pipe cladding is safe for transporting water provided the water was clean to start with. Drinking water should only be obtained from the cold tap.