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.
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.