Copper to steel/iron in a closed loop system

Solid_Fuel_Man

What is everyone's opinion on connecting copper to iron/steel in a closed loop hydronic heating system.  Boiler to piping, air scoop to piping, iron flow checks, the list goes on and on.  I've heard to use anything from a brass valve in between to dielectric unions to just thread 'em together and forget about it. 

Has anyone seen leaks from galvanic corrosion due to the connection of these different metals or is it ok?

 Thanks for everyone's experience!!!!

Taylor

Ron Jr._3

Not a problem

We transition directly from iron or steel to copper around 3 to 5 times per boiler install . And remove about the same amount of transitions with the old unit .  Never seen corrosion due to dissimilar metals . The only time I've seen a leak is because someone didn't tighten the adapter enough . 

nicholas bonham-carter

Dissimilar metals causing problems?

I think the greatest problems may have come about when galvanized pipes were connected directly to copper with no transition fitting. The reaction of zink and copper could be stronger than that of straight iron and copper.

Here is my new theory on the subject: early electric systems were grounded mainly through the water pipes, and if the neutral had a problem, then there would have been a flow of current through the pipes, resulting in an increase in corrosion. Naturally the copper-iron connections would be blamed first.--NBC

icesailor

Copper Adapter leaks:

Or they didn't use Teflon Tape PROPERLY APPLIED and pipe dope/paste, and it was so tight that it leaked anyway, and it took a 3' pipe wrench, backed up, to loosen it up. Then, after cleaning all the hard, dried up pipe dope out of the threads, properly applying Teflon Tape and Pipe Dope, you tighten it with a 18" pipe wrench and it doesn't ever leak again.

My experience.

Solid_Fuel_Man

Cu / Fe

It seems to be a debated topic elsewhere, some heating codes requiring them, and engineers as well.  We all know the difference between engineers and real world experience.  I can see the use of dielectric unions on water heaters etc. oxygenated water.  I just wasn't real keen on using dielectric unions on 190F water, seems like a leak waiting to happen in a few years. 

Ice, I like Gasoila with regular white Teflon, but have had good experience with the thicker pink Teflon as well.  Always open to other suggestions, as I'm just a "hobby heater/plumber" it's whatever pays the bills at this point.  It's so slow around here, I miss the days of the phone ringing off the hook, well sometimes.

Taylor   

gennady

ferrous to non ferrous connections

all ferrous to non ferrous connections must be done with brass fitting or brass nipple or brass valve  and so on (always brass). Do not use dielectric unions, they are always leaking.

Using teflon as an insulator is a bad idea, because tread connection in a sense is welded connection, and joint seals when metal is pressed against metal with such a force than molecules diffusion starts to take place between joining surfaces. This is a reason why pro dope is the best pipe dope, it consists from oil (lubrication) and abrasive ( cleaning unevenness of surfaces to allow metals better contacting each other)

gennady

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duplicate

Solid_Fuel_Man

Conflicting information....

Gennady have you seen evidence of electrolysis, or galvanic corrosion upon taking a direct cu/fe joint apart in a closed loop system?  I know any of us with good piping practices can thread them together and they won't leak, however I'm interested in whats down the road in 20+ years.  Is the oxygen depleted water going to cause any kind of reaction?  I'm just curious....  water conditions must play some type of roll I'd assume as well. 

Also, a bit off topic, but I've read of using TSP to clean the initial system.  Add the prescribed amount per volume, then what?  Is this common practice?  Heat it up, circulate it, flush it, or leave it in?  Sorry for the questions, I just want good info, and good practice.

Thanks my good men!!

Taylor 

gennady

evidence of corrosion

Sure i'v seen it . It really does not matter if system closed or open, because this is electro-chemical nature of corrosion, not presence of oxygen, i m posting picture of corrosion of job, done by another contractor 5 years ago.

gennady

better picture

el corrosion

gennady

TSP

No, i v never used TSP and do not have opinion on that matter.

Cheers

icesailor

Copper/Steel:

I guess my $300 True RMS Multimeter is junk. Even on the highest Ohm scale, I get a low resistance reading on every copper to steel or copper to cast iron fitting done as I have done for over 40 years with Teflon tape.

And I guess that I have been misinformed about how Teflon Tape works.

I watched a TV plumber Guru show someone how to apply Teflon Tape to a fitting so it wouldn't leak and in an application that needed it. HE INSTALLED THE TAPE WRONG!!!!  BACKWARDS!!!! If HE can't or doesn't know how to apply it correctly, how many other professionals don't apply it properly or applied it improperly, had a leak and never used it again.

In the works of male/female pipe connections, it isn't a perfect fit. Pipe thread sealant fills the voids of excessive tolerances. It is still metal to metal in most of the connection. Put a Ohm Meter in a can or pipe dope and see what kind of reading you get.

I see a guy around who does a lot of heating (I understand). He uses a lot of Rectorseal #5. I know, because he has it all over his clothes. It doesn't come out in the wash. There is so much #5 on his clothes that I would bet that his pants could stand up by themselves. And his pants are clean.

How much money do I have to spend to get a True RMS Multimeter that will show that Teflon Tape is a electrical barrier in threaded connections? I've never seen it. But is someone says it is so, it must be so. They must know what they are talking about.

Off topic but, if #5 can't be washed off, and PVC cleaner won't clean it off, why is it OK to use #5 on oil and Rectorseal #100 with Virgin Teflon can.t be used? You can wash it off your clothes and not be known as "#5"?

Larry Weingarten

teflon vs electricity

Icesaiilor: I've had the same discussion for years, people telling me sacrificial anodes won't work if I use teflon to install them.  My (cheaper) meter tells me there is very little resistance across the joint.



The TV plumber must have been watching his image in the monitor when applying teflon.  That must be why he put it on backwards.  Must be!  :~)



Yours,  Larry

icesailor

Reverse images:

Larry,

There was an image on his shirt. It was not reversed. I would have noticed it.

icesailor

Copper to Steel Connections:

Gennady,

I see that all the time now. Now that the water heater manufacturers switched to dialectic nipples instead of letting installers use copper agapter into the top of the tanl.

It doesn't matter how you make up the connection, it will leak over time. I never had that problem with CopXMPT adapters into the top of hot water tanks. Only with Copper X FPT adapters.

gennady

corrrosion

in this particular case somebosy installed galvanized nipple between copper adapter and stainless steel tank. we replaced it with brass nipples and it will last as long as tank will. 

Solid_Fuel_Man

FPT copper

I've seen that too many times, I have always thought it was the softer copper expanding over time.  The steel nipple heating and expanding making the copper do the same only when the connection cools the steel contracts and the copper does not. 

Taylor

bob_46

FE / CU

I agree with Ron 100% . Did anyone ever look at a shell and tube heat exchanger

with those hundreds of copper tubes rolled in intimate contact with a steel tube sheet.

No brass no teflon no dielectric.



Triad Boiler puts a couple of tablespoons of TSP in their boilers before shipping.