Re: corroded water lines
Beanland, thanks, that is a good comment.
I have a detailed study by the american water works associaiton on corrosion in water lines. Nearly all the time corrosion is due to DC currents, not AC. The DC current can be away or toward the house, If away from the house its removing material from the line.
DC power supples, variable speed fans and etc are the cause. Its most likely to be a problem if you have a metallic underground water service line. Often installing a non metallic pipe section will cure the problem.
Keep in mind if this is an older home the ug water line may be the only grounding electrode, the nm pipe section would have to be installed so that ten feet of ug metallic pipe remain in contact with the earth.