# Dissimilar metals in a closed heating system...



## Jklsr55

Another question about something I read...

I have always used di electric unions on heat piping when a transition from steel to copper was called out. I have read online in different places and even heard di electric unions are not unnecessary in a closed loop system. Any thoughts??


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## AlbacoreShuffle

Jklsr55 said:


> Another question about something I read...
> 
> I have always used di electric unions on heat piping when a transition from steel to copper was called out. I have read online in different places and even heard di electric *unions are not unnecessary* in a closed loop system. Any thoughts??


" Not Unnecessary" ?
I guess that means they are necessary.
I almost always use a dielectric union when going from Galv to copper.
If not the union then a brass nipple.


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## Catlin987987

I have never installed them and have rarely seen them installed. Most of the systems we work on are 30+ Years old and I have yet to see any consequences.


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## Jklsr55

*Catlin*



Catlin987987 said:


> I have never installed them and have rarely seen them installed. Most of the systems we work on are 30+ Years old and I have yet to see any consequences.


So in your experience if I were to (for instance) transition from say a copper FIP to a nominal, black , typical gas type steel pipe with an ips threaded end in a closed loop system I would see little or no dissimilar metal reaction? As I stated I am installing a commercial heating system using threaded black pipe in lu of copper. I would like the option of going to copper of room gets tight (like fitting up the radiation in a small corner for instance)...


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## Catlin987987

Jklsr55 said:


> So in your experience if I were to (for instance) transition from say a copper FIP to a nominal, black , typical gas type steel pipe with an ips threaded end in a closed loop system I would see little or no dissimilar metal reaction? As I stated I am installing a commercial heating system using threaded black pipe in lu of copper. I would like the option of going to copper of room gets tight (like fitting up the radiation in a small corner for instance)...


Correct, in appartment buildings that have IP as mains, with copper in the suites. MIPs into the Steel Tees


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## Gettinit

Jklsr55 said:


> So in your experience if I were to (for instance) transition from say a copper FIP to a nominal, black , typical gas type steel pipe with an ips threaded end in a closed loop system I would see little or no dissimilar metal reaction? As I stated I am installing a commercial heating system using threaded black pipe in lu of copper. I would like the option of going to copper of room gets tight (like fitting up the radiation in a small corner for instance)...


I also have not seen any problems at the transitions in closed systems. Don't be lazy, keep it all steel.


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## Catlin987987

Gettinit said:


> I also have not seen any problems at the transitions in closed systems. Don't be lazy, keep it all steel.


How would you pipe the copper rads into steel?


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## Gettinit

Catlin987987 said:


> How would you pipe the copper rads into steel?


I see no mention of copper baseboards. I only saw mention of him using copper in tight quarters. I suppose I would transition with a copper male adapter so I could use a union.

Many areas will still insist on dielectric unions BTW.


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## Catlin987987

Gettinit said:


> I see no mention of copper baseboards. I only saw mention of him using copper in tight quarters. I suppose I would transition with a copper male adapter so I could use a union.
> 
> Many areas will still insist on dielectric unions BTW.


Your telling me in high rises in your area there are dielectric unions on every suite on baseboard heating. Thats leaks waiting to happen.


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## Gettinit

Catlin987987 said:


> Your telling me in high rises in your area there are dielectric unions on every suite on baseboard heating. Thats leaks waiting to happen.


I am saying it is code and it happens to be enforced, particularly in commercial applications. A new building at Wake Forest has dielectric unions in it at every transition. Do I think it is necessary, no.


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## rjbphd

Never, never, ever, NEVER use die electric union craps on heating system!! Be a man, always use male copper adt into female thread....


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## rjbphd

Gettinit said:


> I am saying it is code and it happens to be enforced, particularly in commercial applications. A new building at Wake Forest has dielectric unions in it at every transition. Do I think it is necessary, no.


 That's a bullsh!t code, its pretty obvilus(sp) that its wriiten by a plumber instead of a hydronic heating team..


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## Gettinit

rjbphd said:


> That's a bullsh!t code, its pretty obvilus(sp) that its wriiten by a plumber instead of a hydronic heating team..


I would be happily surprised if it were even written by a plumber. :whistling2::laughing:


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## OldSchool

Closed system any piping material can be directly joined


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## Jklsr55

Gettinit said:


> I also have not seen any problems at the transitions in closed systems. Don't be lazy, keep it all steel.


It has ZERO to do with laziness... Why would anyone even question a transition if it weren't necessary... not to mention take time out of my day to stick my toes in the water around here and take the chance of someone calling me stupid and questioning my aptitude...


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## Gettinit

Jklsr55 said:


> It has ZERO to do with laziness... Why would anyone even question a transition if it weren't necessary... not to mention take time out of my day to stick my toes in the water around here and take the chance of someone calling me stupid and questioning my aptitude...


Why is it necessary? You didn't say it was a copper convector. If they are then you have to but it would look better, IMO, if it were not done until you get to the unit. People on here might bust your balls but I don't think anyone will call you stupid. FYI, just don't say you are number 1....:laughing:


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## Fast fry

What's a union?


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## 6th Density

So at least explain yourselves, Why?
In military construction around here, dissimilar metal is just that and they want dielectric unions on all dissimilar metals PERIOD.
They've even hit us in the past at my old company for not using dielectric unions at cast iron to copper trap arm transitions. 2", 1-1/2", and 1-1/4" dielectric unions can do some damage to a budget.

I'm all for hard piping the system. But are you guys saying that in a closed loop hydronic heating system, with built in corrosion inhibitors, you'd bet on a hard piped brass or stainless steel transition over a rubber washer in a dielectric union? I'm mean how many of you have seen these dielectric unions fail? 

Just curious...


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## theplumbinator

They are not necessary in a closed loop systems very unlikely to have an issue with electrolysis unless you were changing the water in the boiler every day, not very common in a hot water boiler. A boiler in a way treats the water to a degree once its been in the system awhile. One reason why the inside of a hot water boiler is usually way cleaner than steam boiler where your adding fresh water all the time and being open to the atmosphere. Oxygen is the enemy in a hot water system causes rust , mud and electrolysis. maybe over a few decades you may develop a problem at joint of two dissimilar metals but thats job security for the next generation of mechanical contractors to worry about. I wouldn't recommend installing a hot water heater without dilectric unions but thats a whole different animal.


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## theplumbinator

6th Density said:


> So at least explain yourselves, Why?
> In military construction around here, dissimilar metal is just that and they want dielectric unions on all dissimilar metals PERIOD.
> They've even hit us in the past at my old company for not using dielectric unions at cast iron to copper trap arm transitions. 2", 1-1/2", and 1-1/4" dielectric unions can do some damage to a budget.
> 
> I'm all for hard piping the system. But are you guys saying that in a closed loop hydronic heating system, with built in corrosion inhibitors, you'd bet on a hard piped brass or stainless steel transition over a rubber washer in a dielectric union? I'm mean how many of you have seen these dielectric unions fail?
> 
> Just curious...


Copper to cast iron why wouldn't you use a no-hub, mission, or banded (whatever you prefer to call them) coupling? That way metal is only touching rubber plus they are way easy to remove later down the road when the metal trap eventually fails.


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## Brian Ayres

6th Density said:


> I'm mean how many of you have seen these dielectric unions fail?
> 
> Just curious...


Here in Oregon speaking strictly on domestic hot water and cold water I believe just about every dielectric union I've come across has failed before the piping it was attached to. Our company has had a policy for 20+ years that they are not used.... if a dielectic connection is needed, a brass nipple with a copper FIP is used. 

On a closed loop heating system dielectic connections aren't typically used. Copper right into the black iron pipe....


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## 6th Density

theplumbinator said:


> Copper to cast iron why wouldn't you use a no-hub, mission, or banded (whatever you prefer to call them) coupling? That way metal is only touching rubber plus they are way easy to remove later down the road when the metal trap eventually fails.


To the Core of Eng., specs are specs. That's not a good enough argument. Don't forget, if you protest too much they will make it their mission in life to see what else they can find that doesn't agree with the specs. Generally those specs that are written somewhat vague and open to opinion to whoever the inspector is. On some bases (one in particular around here) it doesn't take much to quickly insert your foot in your mouth.


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## theplumbinator

I wouldn't have to make that argument with the inspectors interpretation of the code here, they are code where I work. But I agree with you its not worth making fuss over those guys can Make your life a living hell if you attempt to challenge their knowledge.


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## rjbphd

If that the case, I'll ask the inspector a few simple questions and if they can't answer to proven known facts, I tell them to stick it up in their .....


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## theplumbinator

Im not that bold with those guys yet. Im sure as I get older and more bitter there will come a day when I unleash on an inspector.


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## wundumguy

Better make sure you understand how it works in your area. Around here, letting it go on an inspector is usually a really bad career move.


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## theplumbinator

I realize that probably y I haven't made it a point to piss in their cherrios, an inspector has the power to make my life very difficult. Cant wait till I finish school so I can be one myself. Im not going to be one of those power hungry jerk inspectors either just want to do my job get paid not break my back and knees anymore and uphold the plumbing code.


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## gtmechanic

I never use dielectric unions. I always use brass fitting or valve. The proof is that brass valve can be used on copper and steel. so if one end of brass fitting is connected to steel and another to copper, there is no problem.


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## Fast fry

Just a reminder , there is usually one reason why an inspector is an inspector............failed tradesmen. We got one guy here and EVERYTIME I go to the suppliers I hear all the contractors bad mouthing this yahoo and even h.o. Going down to the city to complain about him. Usually the case of the kid who got picked on in school or work, now with a little bit of authority.


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## AlbacoreShuffle

Fast fry said:


> Just a reminder ,* there is usually one reason why an inspector is an inspector............failed tradesmen.* We got one guy here and EVERYTIME I go to the suppliers I hear all the contractors bad mouthing this yahoo and even h.o. Going down to the city to complain about him. Usually the case of the kid who got picked on in school or work, now with a little bit of authority.


Thats not the case in many cases.
I have a buddy that has some health issues, and working in the field all day just isn't going to happen.
Hes been in the plumbing business for his entire adult life. ( he's 55 yo )
Plumbing is all he knows.
He just closed his shop down and now is a plumbing inspector for a local city.


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