I have the same study that Mike Holt mentioned by the AWWA. While AC current will not cause corrosion of metallic water piping DC will. And it can be away from the house or towards the house. If away from the house, it will cause corrosion of the copper piping. If the piping is continuous to the water main in the street, the AWWA (American Water Works Association) recommends installing a 6-12" section of nonmetallic pipe at least 10 feet from the house (so the water service line will still be effective as grounding electrode)
DC current can be caused from electric drills or hair dryers.
Also, as I do a lot of work for a large municipal water system, and in our system we have a corrosion control treatment facility that raises the pH of the water from 7.5 to 8.5, as the low pH is corrosive to the lead and copper. This is a requirement by the EPA to treat some water if its considered aggressive and can cause corrosion.
Check with your water supplier, see what the pH of the water is, and if it changes from season to season.
Your answer will depend a lot on how large the supplier is, and hopefully they will have a water quality technican you can discuss this with.
Tom Baker
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