The solubility of metallic lead (and its related oxidation products) depends on the ph of the water it's in contact with. If the ph is high enough, the lead won't dissolve, but if it drops below a certain point, then lead ions go into the solution. That is what happened recently in Flint Michigan, causing a major public health emergency. See http://cen.acs.org/articles/94/i7/Le...Tap-Water.html