Jeff Wisnia wrote:
Sac Dave wrote:

"Big Al" wrote in message
...

Question: Have a 3/4" copper to galvanized pipe junction, has a 6"
brass nipple between them. Is this the proper way to do this to
prevent electrolysis?

Other than on a water heater, when would one use an electrically
isolated union? And why?

Al


Brass is neutral metal and will work.



I'd love to hear what makes you think brass is a "neutral metal", Sac Dave.

Have you ever even bothered to look at a galvanic table?

Try spending some time reading articles like this one:

http://tinyurl.com/5sekem

before you hand out totally incorect advice.

*******

Regarding the OP's mention of water heaters, the use of dielectric
unions on them is passe, as stated by Rheem in this bulletin:

http://tinyurl.com/5e56ub

Although I realize that this is not a group organized to further
literacy the first sentence of the Rheem bulletin is not one that
portends great understanding.

The second sentence is more worrisome. "... a shut-off valve in at
least the cold inlet waterline is recommended,..." Where would another
other shut-off valve be placed? In the only other waterline, the hot
water outlet? This is an implied prescription for a bomb, and violates
every plumbing code that I'm familiar with.

The rest of the piece is an attempt at explaining electrochemistry which
is much better done in a plethora of texts.


Jeff