Andy M-S wrote:
I recently took a look at our water heater (3-4 years old, gas), and
the hot pipe coming out of the top is covered with the kind of
corrosion I often associate with car batteries. Is something not
properly grounded? How much of a problem do I have?


Are you referring to a white powdery substance?

It may just be the result of the last installer using a mildly corrosive
flux when soldering a fitting and not wiping it off the pipe well enough
before he left.

Go at it with some warm water and detergent and a kitchen "scrub
sponge". If you clean the pipe off well it'll likely not return.

HTH,

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."