I own an older home, and there are three places that I can see where the electrical system is directly grounded to the copper water pipes. One of those wires comes directly from the electrical panel, but two others seem to come from individual circuits. The one that comes from the panel is directly connected to the water pipe where it enters the house. Right after the water main enters the house - right after the shutoff - the copper changes to PVC for about 15 feet, then back to copper. Are the circuits that are grounded to the copper pipes "past" the PVC actually grounded? I am asking because I would like to replace some of the copper with PEX, but I'm not sure what to do with the grounding wires.