As for pitting in the water lines, that is typically caused where the water heaters coating on the core has been compromised (by age and electrolisys (spelling?) typically in an electric water heater where anode replacement was not kept up). The iron particles from the deteriating water heater then migrate into the copper water lines where gravity pulls them to the bottom of the pipes when waterr is not flowing. The iron comes in contact with the copper (dissimilar metals) and causes the pitting.
Shane
