Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 8,803
Default Mixing metals in water pipes

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?

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

Is it important to use copper hangers for copper pipe?

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


  #2   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 4,926
Default Mixing metals in water pipes

On Apr 15, 3:14*am, "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?

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

Is it important to use copper hangers for copper pipe?

Seattle water, if it matters.http://www.ci.seattle.wa.us/util/ste.../@spu/@ssw/doc...


I think the copper wire allows the pipe to continue to be a ground,
when someone used copper to galvanised on my pipe it deteriorated and
looked bad fast and I replaced it, on a water heater a thermal break
is needed to help to keep heat in the heater.
  #3   Report Post  
Posted to alt.home.repair
dpb dpb is offline
external usenet poster
 
Posts: 12,595
Default Mixing metals in water pipes

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?


Not for corrosion protection, no--the wire is a grounding wire
completing a ground around the dielectric path.

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?


Cu/brass is ok...

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


The less noble metal is more attacked so steel (Fe) is preferentially
the target. But, there is often less actual Cu physically so it may be
the copper side that actually fails first. Upshot is, it can be either.

Is it important to use copper hangers for copper pipe?


Yes.


A link that has good discussion of galvanic corrosion in water systems
-- it's specifically addressing fire protection systems but the
principles are the same and it's as good/cogent discussion I've seen...

http://www.copper.org/applications/p...r_systems.html

--
  #4   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 8,803
Default Mixing metals in water pipes


"dpb" wrote in message ...
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?


Not for corrosion protection, no--the wire is a grounding wire completing a
ground around the dielectric path.


Right - but does it defeat the protection offered by the dielectric union?


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?


Cu/brass is ok...


Even when the other end of the valve is connected to galvanized outside pipe?


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


The less noble metal is more attacked so steel (Fe) is preferentially the
target. But, there is often less actual Cu physically so it may be the copper
side that actually fails first. Upshot is, it can be either.

Is it important to use copper hangers for copper pipe?


Yes.


A link that has good discussion of galvanic corrosion in water systems -- it's
specifically addressing fire protection systems but the principles are the
same and it's as good/cogent discussion I've seen...

http://www.copper.org/applications/p...r_systems.html


Thanks for the reference.


  #5   Report Post  
Posted to alt.home.repair
dpb dpb is offline
external usenet poster
 
Posts: 12,595
Default Mixing metals in water pipes

Bob F wrote:
"dpb" wrote in message ...

....
Not for corrosion protection, no--the wire is a grounding wire completing a
ground around the dielectric path.


Right - but does it defeat the protection offered by the dielectric union?


No, galvanic action is a direct contact. The ground wire, while there
is a potential yes, being dry is far less susceptible to the corrosion
and it's there where it can be seen, anyway. The dielectric between the
two water pipes themselves is still between the two dissimilar metals.
It would be nice if they were all the same material, but it's the lesser
of the evils.

Cu/brass is ok...


Even when the other end of the valve is connected to galvanized outside pipe?


Well, no, that's a different connection--it's a direct connection
between the two dissimilar metals so strictly there should be one at
each junction where switching. As noted, brass being a mostly copper
alloy is near enough in potential to not be a problem.

--


  #6   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 1,300
Default Mixing metals in water pipes

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.

  #7   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 1,300
Default Mixing metals in water pipes

dpb wrote:

Bob F wrote:

"dpb" wrote in message ...


...

Not for corrosion protection, no--the wire is a grounding wire
completing a ground around the dielectric path.



Right - but does it defeat the protection offered by the dielectric
union?



No, galvanic action is a direct contact. The ground wire, while there
is a potential yes, being dry is far less susceptible to the corrosion
and it's there where it can be seen, anyway. The dielectric between the
two water pipes themselves is still between the two dissimilar metals.
It would be nice if they were all the same material, but it's the lesser
of the evils.



I'm afraid you are wrong there, dpb. the electrical connection between
the two dissimilar metals does NOT have to be in the (wet) electrolyte area.

Just visualize a strip of copper and a strip of zinc joined together at
one of their ends and spread apart at the other. Immerse the spread ends
of the strips in a weakly acidic electrolyte, with the joined ends above
the liquid level.

Doing that effectively creates a battery, with a dead short across its
positive and negative terminals.

The zinc will corrode away pretty fast, even though the "touching" parts
aren't wet.

Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*1012 furlongs per fortnight.




--

Cu/brass is ok...



Even when the other end of the valve is connected to galvanized
outside pipe?



Well, no, that's a different connection--it's a direct connection
between the two dissimilar metals so strictly there should be one at
each junction where switching. As noted, brass being a mostly copper
alloy is near enough in potential to not be a problem.

--




  #8   Report Post  
Posted to alt.home.repair
dpb dpb is offline
external usenet poster
 
Posts: 12,595
Default Mixing metals in water pipes

Jeff Wisnia wrote:
....

I'm afraid you are wrong there, dpb. the electrical connection between
the two dissimilar metals does NOT have to be in the (wet) electrolyte
area.


I _said_ there's still a potential. But it's still visible for
inspection and it's still the lesser of the evils -- the electrical
ground has to be made.

--
  #9   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 8,803
Default Mixing metals in water pipes


"dpb" wrote in message ...
Bob F wrote:
"dpb" wrote in message ...

...
Not for corrosion protection, no--the wire is a grounding wire completing a
ground around the dielectric path.


Right - but does it defeat the protection offered by the dielectric union?


No, galvanic action is a direct contact. The ground wire, while there is a
potential yes, being dry is far less susceptible to the corrosion and it's
there where it can be seen, anyway. The dielectric between the two water
pipes themselves is still between the two dissimilar metals. It would be nice
if they were all the same material, but it's the lesser of the evils.


Just like a battery with a short across its terminals? I don't understand why
this is not a problem.


Cu/brass is ok...


Even when the other end of the valve is connected to galvanized outside pipe?


Well, no, that's a different connection--it's a direct connection between the
two dissimilar metals so strictly there should be one at each junction where
switching. As noted, brass being a mostly copper alloy is near enough in
potential to not be a problem.


But the brass is not similar to the galvanized pipe screwed into it.


  #10   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 8,803
Default Mixing metals in water pipes


"dpb" wrote in message ...
Jeff Wisnia wrote:
...

I'm afraid you are wrong there, dpb. the electrical connection between the
two dissimilar metals does NOT have to be in the (wet) electrolyte area.


I _said_ there's still a potential. But it's still visible for inspection and
it's still the lesser of the evils -- the electrical ground has to be made.


They attach a zinc block to metal parts underwater on boats - sometimes even
with a wire going to an above water connection point. This reduces corrosion of
all the metal connected to it. The corrosion does not just occur at the
connection point. Connect a metal from the other end of the chart the same way -
everything would corrode faster, right?




  #11   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 8,803
Default Mixing metals in water pipes


"Jeff Wisnia" wrote in message
news:[email protected]...
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.


I am surprised the anode in the tank did not protect the nipples.

Do you suppose the the anode was similarly degraded? Or was it already gone?


  #12   Report Post  
Posted to alt.home.repair
dpb dpb is offline
external usenet poster
 
Posts: 12,595
Default Mixing metals in water pipes

Bob F wrote:
"dpb" wrote in message ...
Jeff Wisnia wrote:
...

I'm afraid you are wrong there, dpb. the electrical connection between the
two dissimilar metals does NOT have to be in the (wet) electrolyte area.

I _said_ there's still a potential. But it's still visible for inspection and
it's still the lesser of the evils -- the electrical ground has to be made.


They attach a zinc block to metal parts underwater on boats - sometimes even
with a wire going to an above water connection point. This reduces corrosion of
all the metal connected to it. The corrosion does not just occur at the
connection point. Connect a metal from the other end of the chart the same way -
everything would corrode faster, right?


The also make compatible metal grounding clamps.

However, I've ground connections of copper to galvanized and black iron
that have been in place for 40 years or longer and they simply have not
been a problem.

--
  #13   Report Post  
Posted to alt.home.repair
dpb dpb is offline
external usenet poster
 
Posts: 12,595
Default Mixing metals in water pipes

Bob F wrote:
"dpb" wrote in message ...
Bob F wrote:
"dpb" wrote in message ...

...
Not for corrosion protection, no--the wire is a grounding wire completing a
ground around the dielectric path.
Right - but does it defeat the protection offered by the dielectric union?

No, galvanic action is a direct contact. The ground wire, while there is a
potential yes, being dry is far less susceptible to the corrosion and it's
there where it can be seen, anyway. The dielectric between the two water
pipes themselves is still between the two dissimilar metals. It would be nice
if they were all the same material, but it's the lesser of the evils.


Just like a battery with a short across its terminals? I don't understand why
this is not a problem.

Cu/brass is ok...
Even when the other end of the valve is connected to galvanized outside pipe?

Well, no, that's a different connection--it's a direct connection between the
two dissimilar metals so strictly there should be one at each junction where
switching. As noted, brass being a mostly copper alloy is near enough in
potential to not be a problem.


But the brass is not similar to the galvanized pipe screwed into it.


I just go through saying that -- I was talking of the brass/copper
junction. If you have a brass/galvanized on the other end, it should
also be a dielectric connection.

There are compatible-metal grounding clamps available.

My experience has been however, that the grounding of a copper wire to
either galvanized (scrape through to the underlying iron) or black pipe
has not been a real problem in practice. It just doesn't seem to be an
issue that I've observed at that point.

--
  #14   Report Post  
Posted to alt.home.repair
external usenet poster
 
Posts: 1,300
Default Mixing metals in water pipes

Bob F wrote:

"Jeff Wisnia" wrote in message
news:[email protected]...

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.



I am surprised the anode in the tank did not protect the nipples.

Do you suppose the the anode was similarly degraded? Or was it already gone?




I did say that I'd "changed out" (replaced) the heater, and the leak
developed a few month's later. So the anode rod was new.

The adonde doesn't protect the nipples because of the galvanic current
distribution through the electrolyte. It's effect can't "reach up" into
the nipples.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.98*10^14 fathoms per fortnight.
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
mixing paint with water benpost UK diy 2 March 21st 08 01:01 PM
Can the repairs to the City Water Main Cause Burst Pipes through Water Hammer [email protected] Home Repair 7 August 11th 06 02:12 AM
Electric Water Heater Grounded to Copper Water Pipes? [email protected] Home Repair 4 October 30th 05 06:23 PM
How do heavy metals dissolved in water param UK diy 6 September 2nd 05 10:43 PM
Freezing Pipes or Pipes frozen could the Instant Hot Water Recirculator from RedyTemp work [email protected] Home Repair 1 January 11th 04 12:18 PM


All times are GMT +1. The time now is 05:03 AM.

Powered by vBulletin® Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright 2004-2023 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"