What might cause slight corrosion atop a tankless water heater's copper topped element assembly?

I checked all the grounding and reconnected the two element assembly grounding wires and ensured proper tightening. Then, I checked the grounding wire from the tankless unit to my breaker box. I then switched this ground wire from the neutral bar to the grounded bar. There is absolutely no bonding/grounding to a water pipe! I cleaned off all the corrosion.

Could the loose ground wires have caused the corrosion? I began the grounding issue because I discovered a faint pale green stain in one bathroom sink and suspected electrolysis. I have a whole house water processing system installed. I called the manufacturer but, was placed on hold for over 20 minutes. I eventually hung up.

  • My apologies, if i used incorrect terminology and/or failed to put info in the proper sequence.
    Aug 15, 2013 at 18:59
  • 1
    Pictures are always helpful.
    – Tester101
    Aug 15, 2013 at 19:29
  • What is a copper topped element assembly? Is that inside or outside the unit?
    – wallyk
    Aug 16, 2013 at 3:40

1 Answer 1


There are any number of things that could cause corrosion: - leaks or other water on the corroded surface - grounding or some other electrical field - ambient corrosive elements in the air (water, overspray from other projects)

I think you did the right thing by checking and fixing your grounds. That might not be the root cause, but it doesn't hurt to have everything properly grounded.

Does your water heater have a sacrificial anode? They can be somewhat tricky to inspect and replace but if its old and used up then corrosion might attack other parts.

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