You need to try to find out if the heavy metal is from your water source, or from your kettle or chiller or other equipment, or a combination. Not sure how this would be accomplished -- are there inexpensive water tests for heavy metals? Then replace whatever water or equipment is causing the problem.
Sorry I never really got into heavy metal. Metallica is about as close as I get. Well, some of the new Queensryche ain't bad either, if it counts(?).