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Water Header: Dielectric fitting too, or just the bonding cable JayN 07-23-2008
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Posted by JayN on July 23, 2008, 4:17 pm


I'm having a new water heater installed soon. I'm told my state (NJ)
requires a bonding cable be installed between the hot and cold water
lines.

I'm wondering if there is any benefit to also requesting a dielectric
fitting be installed intstead of standard copper fittings. If a
bonding cable is used, does this make the the dielectric fitting
unnecessary if my goal is to prevent corrision at the connections?
Is there any benefit to also requesting the use of a dielectric
fitting?

Thanks,

Jay

Posted by ransley on July 23, 2008, 4:37 pm


> I'm having a new water heater installed soon. =A0I'm told my state (NJ)
> requires a bonding cable be installed between the hot and cold water
> lines.
>
> I'm wondering if there is any benefit to also requesting a dielectric
> fitting be installed intstead of standard copper fittings. =A0If a
> bonding cable is used, does this make the the dielectric fitting
> unnecessary if my goal is to prevent corrision at the connections?
> Is there any benefit to also requesting the use of a dielectric
> fitting?
>
> Thanks,
>
> Jay

A fitting to consider is a thermal break so you dont loose heat out
the pipes

Posted by Jeff Wisnia on July 23, 2008, 4:51 pm


JayN wrote:
> I'm having a new water heater installed soon. I'm told my state (NJ)
> requires a bonding cable be installed between the hot and cold water
> lines.
>
> I'm wondering if there is any benefit to also requesting a dielectric
> fitting be installed intstead of standard copper fittings. If a
> bonding cable is used, does this make the the dielectric fitting
> unnecessary if my goal is to prevent corrision at the connections?
> Is there any benefit to also requesting the use of a dielectric
> fitting?
>
> Thanks,
>
> Jay

If your place is plumbed with copper then you'll do best to stick with
all copper/brass right up to the heater tank's cold and hot ports.

Rheem stopped recommending dielectric unions on their water heaters a
few years ago:

http://home.comcast.net/~jwisnia18/temp/Rheem_unions.pdf

I'm sure I've mentioned this before, but about four years ago when I
last replaced our electric water heater, I slavishly installed a pair of
dielectric unions at the inlet and outlet ports, replacing the all
copper ones which were there before. I used a pair of short iron nipples
between the tank ports and the iron sides of the unions. Those nipples
clogged with soft rust and one of them sprang a leak in just a few months.

Here's the leaking nipple, after I sliced it down the midline and
scraped out most of the rust:

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

I thought things through and realized the dielectric unions were
effectively "shorted out" because the heater tank was grounded per code
as was the copper piping in our home, so they weren't helping at all.

I replaced those dielectric unions and the iron nipples with all
copper/brass fittings and things have been fine since.

The insides of the iron nipples took the brunt of the galvanic corrosion
because they were electric field wise "out of sight" of the sacrificial
anode rod in the tank.

Jeff

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

Posted by JayN on July 23, 2008, 5:48 pm


I'm planning on installing an AO smith and in their instructions they
strongly recommend dielectric unions. My pipes are copper. I had
thought the connection on the heater itself is stainless steel, is
that incorrect? Wondering if the treads are wrapped with teflon tape
that the teflon has any dielectric effect? Do you think I should
igore what the Smith manual says:

"NOTE: To protect against untimely corrosion of hot and cold
water fittings, it is strongly recommended that di-electric unions
or couplings be installed on this water heater when connected
to copper pipe."

Jeff

> as was the copper piping in our home, so they weren't helping at all.
>
> I replaced those dielectric unions and the iron nipples with all
> copper/brass fittings and things have been fine since.
>
> The insides of the iron nipples took the brunt of the galvanic corrosion
> because they were electric field wise "out of sight" of the sacrificial
> anode rod in the tank.
>
> Jeff
>
> --
> Jeffry Wisnia
> (W1BSV + Brass Rat '57 EE)
> The speed of light is 1.8*10^12 furlongs per fortnight.


Posted by hallerb@aol.com on July 23, 2008, 8:11 pm


> I'm planning on installing an AO smith and in their instructions they
> strongly recommend dielectric unions. =EF=BF=BD =EF=BF=BDMy pipes are cop=
per. =EF=BF=BDI had
> thought the connection on the heater itself is stainless steel, is
> that incorrect? =EF=BF=BDWondering if the treads are wrapped with teflon =
tape
> that the teflon has any dielectric effect? =EF=BF=BDDo you think I should
> igore what the Smith manual says:
>
> "NOTE: To protect against untimely corrosion of hot and cold
> water fittings, it is strongly recommended that di-electric unions
> or couplings be installed on this water heater when connected
> to copper pipe."
>
> Jeff
>
>
>
> > as was the copper piping in our home, so they weren't helping at all.
>
> > I replaced those dielectric unions and the iron nipples with all
> > copper/brass fittings and things have been fine since.
>
> > The insides of the iron nipples took the brunt of the galvanic corrosio=
n
> > because they were electric field wise "out of sight" of the sacrificial
> > anode rod in the tank.
>
> > Jeff
>
> > --
> > Jeffry Wisnia
> > (W1BSV + Brass Rat '57 EE)
> > The speed of light is 1.8*10^12 furlongs per fortnight.- Hide quoted te=
xt -
>
> - Show quoted text -

I would follow the manufactuers recomendations, dis similiar metals do
wierd things

have you looked at the very high efficency gas water heaters tank type
the 96% efficency ones?

upfront costs are higher but first hour ratings capacity etc are
excellent

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