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
Other than on a water heater, when would one use an electrically isolated
union? And why?
Copper, PEX & PVC all have their place in properly designed &
installed "plumbing" systems.
I have used (& use) all three or a mix of them, depending on the
All three have their advantages & disadvantages (even copper has some
downside, besides cost).
I always favored copper (before & after the recent price spike) but
once I used PEX, my opinion changed.
I still use copper and often do the copper / PEX hybrid thing.
Don't dismiss PEX, cuz' it's plastic or "cheap"...the system has a lot
of advantages over copper, even soft copper.
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:
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:
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.
Since that's how mine is done I'm curious. How is having a shutoff
at the tank any more dangerous than the normal shutoffs at the
Can you cite a code that forbids it? Or better yet- an incident where
a [preferably open as that is the normal state] valve on the hot side
caused an explosion?
I agree that it is a minimal advantage, but I'm glad that whoever did
mine, did it this way. When I work on the hot water lines I
shut just them down.
I won't quibble with you about plumbing codes, as I'm not a mavin about
them, and it is not unreasonable to expect they'd prohibit hot side
shutoff valves on water heaters.
But how did you come up with "This is an implied prescription for a bomb"?
Can you answer these questions?
Do you know what a T&P valve is and why they're code required on water
How is having a closed shut off valve on the hot side of a water heater
significantly different than having all "hot" faucets downstream of the
water heater closed, as they usually are for many hours at a time in an
Now please defend your "bomb" statement.
BTW, dielectric unions do have their uses in specific situations. One
application I remember is the need to use them in natural gas lines when
they enter a building.
Back in the days when all gas mains buried under streets were iron pipe
(pre-plastic pipe era.) "impressed current cathodic protection systems"
were used to prevent corrosion of those mains.
Dielectric unions were installed ahead of the gas lines where they
entered buildings to avoid having gas appliances (such as water heaters)
from shorting those electrified gas mains to ground.
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