black pipe to copper/brass fittings? - indirect piping

steve_173

Where the black pipe runs into the indirect (Superstor) fittings, does one need dielectic unions or some form of brass sacrificial nipple that can be replaced? Right now, I have an iron union directly onto the Superstor.

Henry

Dielectric

It is not necessary

steve_173

?

Because people don't like the tendency for dielectric unions to leak or because there is no benefit to one or some other option in the indirect loop (circulating steam boiler water)?

Steve Whitbeck

iron to brass

iron to brass is OK - copper to brass is OK - iron to copper is NOT OK.

Mark Eatherton

EXCEPT.....

Steve, you said iron to copper is not OK. Unless it is in a closed loop system, then it is acceptible.



To the original poster, stainless steel is neutral to both copper and steel.



In a true di-electric condition (two dissimilar metals in an aqueos (oxygenated) solution, the lesser noble of the two metals will fail. You want to avoid these situations whenever possible. A YELLOW brass fitting will act as a dielectric break, even in an aqueous solution. For example, connecting copper to a glass lined steel tank, use a yellow brass nipple to make the connection, and no dielectric condition will occur. This is an accepted method under both plumbing codes. Dielectric unions, for the most part, are a joke, and actually create their won stray current conditions that causes them to fail.



ME

Steve Whitbeck

Not here

On a comercial boiler install that will not pass code here. You have to either use a die/ union or do what I do and use a brass fitting between the iron and the copper. ( usually a ball valve)

Mark Eatherton

We're saying the same thing Steve...

Brass (whatever, nipple, ball valve, wye strainer, anything brass) between copper and steel tank for example in a POTABLEE water app.. That's what the code says. Your LOCAL code can be "Equal to or more stringent than" the national code, which a dielectric union only WOULD be, but most inspectors understand the intent.



You're not supposed to be running steel pipe in oxygenated water. The reason it is allowed on closed loop systems is because those systems are missing the one critical compound to complete the electrolytic battery, that being oxygen (fresh water or non barrier tubing). As I said, your local code may be more stringent, but again, the  UMC and the I codes allow it. I think fire protection systems are an exception to that rule. But I don't profess to be a FP expert.



ME

Ron Jr._3

Iron to copper is perfectly fine

We install at least 3 copper adapters into steel or cast iron every day . And take apart just as many when removing the old boiler . Never seen a problem at these joints ....... other than the rare occasion someone didn't tighten the fitting enough .



If you're using copper to iron in a potable situation , then you've got more problems than a missing dielectric fitting !