Do I need a dielectric union for my water heater?

[navysuit]

The nipples coming out of the water heater are galvanized with a blue plastic lining. Do I need to add a dielectric union?

[jimbo]

No. Those dielectric nipples provide all you need.

[hj]

Those nipples work the same as a dielectric union, which is to say not very good, or effective, in the first place.

[navysuit]

Those nipples work the same as a dielectric union, which is to say not very good, or effective, in the first place.

What would you recommend I do then? Should I just go with the nipples only? I have heard someone say they replace the galvanized nipple with brass. Is this the best thing to do?

[jadnashua]

Different metals in contact create what amounts to a battery...material moves from one electrode to the other chemically changing the two. This requires intimate contact and a means for the ions to migrate. There is a scale of reactivity. The further apart the two metals are, the higher the reactivity. Steel rusts all on its own. I'd probably pop some brass nipples in there and call it a day. Brass is between copper and iron, so it acts like a moderator and it won't rust all on its own, either.