Electrolysis copper and stainless steel (Update)
#10
  
Will electrolysis happen if copper is attached to stainless steel? Specifically, I have a stainless steel UV light that is piped in a copper system. I’m seeing rust forming on the nipples of the UV light where it’s attached to copper unions. 
I wasn’t the one who installed it, my thought would be to use cpvc where the light is plumbed in. I’m not a big fan of dielectrics as they can still corrode with even of small amount of moisture (like from condensation).

Update:
I called Viqua, the UV light manufacturer and they said the UV light should be plumbed with copper as PVC or CPVC degrades where it’s connected to the light. She said more likely is I have some bad fittings.
They did offer to send a replacement unit free since I’m still in the warranty period. Got to give them credit for some great customer service!
VH07V  
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#11
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
Not sure about electrolysis, but I would think you would want some sort of non-conductive bushing between the dissimilar metals to prevent that going forward.
Benny

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#12
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
A long-ish article describing this corrosion.  It is very a comprehensive discussion.

https://www.phcppros.com/articles/2867-c...ing-piping
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#13
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
It is galvanic corrosion from the two dissimilar metals. You are correct that there needs to be some sort of separation from direct contact.
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#14
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
(02-03-2020, 03:25 AM)EightFingers Wrote: Will electrolysis happen if copper is attached to stainless steel? Specifically, I have a stainless steel UV light that is piped in a copper system. I’m seeing rust forming on the nipples of the UV light where it’s attached to copper unions. 
I wasn’t the one who installed it, my thought would be to use cpvc where the light is plumbed in. I’m not a big fan of dielectrics as they can still corrode with even of small amount of moisture (like from condensation).

Should have dielectric unions. When I see it in a home inspection, corrosion or not, it goes in the report as a defect. There should be a copper ground conductor jumper across the device bonded to both copper pipes. Just like what's required between water heater supply and discharge pipes. You could always use CPVC unions if you are worried about corrosion.
 
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#15
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
Thanks all, just as I was thinking. Cooler’s article helped confirm it. Looks like I’ll be contacting the plumber who installed it.
VH07V  
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#16
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
See OP above for update!
VH07V  
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#17
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
What about a healthy layer of teflon tape? Probably still get some metal to metal contact...
Benny

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#18
  Re: Electrolysis copper and stainless steel (Update) by EightFingers (Will electrolysis ha...)
I'm presently replacing the water pipes in this old house and I've found two connections (They were painted) at the water heater where copper was attached to galvanized fittings. Been like that for at least 30 years I know of and it shows no sign of corroding. Go figure.
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