Bob F wrote:
I've done a bit of research on the subject. They say don't connect copper to
galvanized. Some sites say to use a dielectric union between then. Some say
brass can be used instead. I've seen dielectric unions with a hard copper wire
connected to both pipes - seems like that would defeat the purpose of the union,
but does code require it?

I currently have galvanized pipes with galvanized pipe coming into the house,
and am planning to replace the inside pipes with copper. There is a brass valve
at the entry. Do I need a dielectric union connected to that valve? Or can I
just connect copper to it? Should I use dielectric unions at the water heater?

Rheem says you don't have to. See Page 5, Item 3, end of the fourth
paragraph of this document:

http://waterheating.rheem.com/conten...lecEclipse.pdf

I can testify that using dielectric unions between copper piping and
steel nipples screwed into the inlet and outlet openings of an electric
water heater wasn't the right thing for me to do the last time I changed
out the heater.

While there is no "direct contact" of the copper and steel parts, there
IS an hard electrical connection between the two metals through the code
required electrical ground wire connected to the tank and the similarly
code required grounding of the copper plumbing system.

Within a matter of months one of the steel nipples corroded through, and
both the (inlet and outlet) nipples were filled with "rust" to the point
where water flow was impeded.

I replaced the dielectric unions with copper unions and all copper
connections between them and the tank openings and all's been well since
then.

Here's a photo of the nipple which leaked, taken after I sliced it in
half and scraped out most of the rust inside it:

http://home.comcast.net/~jwisnia18/temp/nipple.html



What really fails when galvanized and copper pipe are connected together? The
copper? The galvanized? The joint itself?

It's usually the steel (galvanized) part. The zinc galvanizing gets
quickly corroded away, then the steel beneath it goes.

Is it important to use copper hangers for copper pipe?

If the area where the pipes are hung has low humidity, so they never
"sweat" then steel hangers can be used. If there is a chance that
moisture will be present, then use copper hangers.


Seattle water, if it matters.
http://www.ci.seattle.wa.us/util/ste...u01_002826.pdf




--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.