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#1
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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
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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
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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
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![]() "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
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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
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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
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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
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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
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![]() "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
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![]() "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
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![]() "Jeff Wisnia" wrote in message news:RfednS_Fr6B3u5jVnZ2dnUVZ_q-jnZ2d@choiceonecommunications... 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
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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
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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
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Bob F wrote:
"Jeff Wisnia" wrote in message news:RfednS_Fr6B3u5jVnZ2dnUVZ_q-jnZ2d@choiceonecommunications... 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. |
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