Similar to this question, I've got severe corrosion on my 4 year old water heater inlet. I was having the heater flushed when this was discovered, and the person flushing it said it was caused by the installer not using a dialectric nipple.

Picture of corrosion

So I contacted the installer, who claims that the copper flex is dielectric so a dielectric nipple is not needed. Is this possibly true? If so, what else could have caused it?

It would be great to know if the original installer is being honest. If they are, I'll have them do the work to fix it. If not, I'll find a new plumber/plumbing company.

  • 1
    This looks more like water is leaking and evaporating and less like galvanic corrosion. I may be wrong, but since this looks like a gas fired water heater and not an electric one, there really shouldn't be the presence of any power accelerating the corrosion this quickly. It's possible that the flue is back drafting and you're getting moisture that condenses on the cold side, but it looks more like hard water (calcium/lime deposits) and that doesn't come from condensation.
    – Dotes
    Oct 27, 2017 at 16:17
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    Thanks for the input. Ironically, the person flushing the water heater was our water softener installer, replacing a recently failed water softener... which means we've never really had hard water running through it, save the past two weeks when our softener was out. It's nice to know the original installer is likely on the up-and-up. Oct 27, 2017 at 16:34

1 Answer 1


My educated guess without being there is that the flex connector joint was not installed correctly or is just leaking. I never liked this type of installation since it was made for the novice and not a professional. I always used hard copper and a non-lead solder containing silver. I also never used galvanized piping, just brass fittings and copper tubing. Whoever installed this did a sloppy, non-professional job.

  • Thanks for the feedback. The installer had no answer for "why" this was happening when I asked what we could do to prevent recurrence, and offered to use brass this time. I'll find somebody new. Oct 27, 2017 at 18:50
  • I agree with @d.george (+1)- this is poorly done and looks like it leaked. Also, they are wrong about the electrolysis issue. Whether it leaked or not, you would have ended up with galvanic corrosion where the copper flex meets the steel pipe. The tee and nipples should have been brass. Oct 27, 2017 at 19:07

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