Mixing black pipe and copper

heatinghelp819

I have a steam boiler that has a nipple attached to it that is rotting/corroded (see pics). I’ve had a few plumbers out who work lots with steam systems in my area to take a look— all will need to replace some of the black pipe (one said possibly the whole H loop) because they won’t be able to only change the nipple for various reasons, and all want to replace at least partially with copper in some way. They say copper is best for the pipes that are under water as they won’t rot like black pipe will. I read that copper is finicky with steam systems (though I’m not sure if that applies to the wet pipes) and that mixing copper and black pipe is a bad idea (I think one plumber says he avoids issues by doing something special with the fittings but I can’t remember what exactly he said). Should I insist on black pipe and risk rotting again or go with copper (and risk a leak?) as they all recommend?   

STEVEusaPA

Copper is usually ok below the water line. But that's not's what is wrong with your second picture.

heatinghelp819

Do I need to make sure anything special is done where the copper is joined to existing black pipe to avoid issues?

And ok I’ll take the bait knowing that I won’t be fixing more than what’s necessary right now - what’s wrong?

mikeapolis

Check out this article: https://heatinghelp.com/systems-help-center/copper-tubing-and-steam-systems/

heatinghelp819

Thanks for the link; I had read this before which was the source of my questions when the plumbers suggested copper. I guess i am wondering if someone here could tell me what I should ensure they’re using/doing where the copper connects to the black pipe. Or should I just insist on black pipe and pray it doesn’t rot again?

ChrisJ

I used all copper below the water line, and even my equalizer is copper. Nothing special, just good heavy fittings.

That being said, how long did it take yours to rott?

heatinghelp819

I’m not sure; we’ve been in the house 5 years. Knew the owners who were here a few years before that. First issue with corrosion. I forget how old the boiler is. 

Is yours copper for wet and black pipe for steam? If so what was done at their junction?

JUGHNE

Some use a brass ball valve (used for isolation flushing etc.) for the transition.
Some use brass nipples for the transition.
Some use a heavy USA made blk nipple into the boiler, could be SCH 80 even.
Some use brass into the boiler for any boiler connection.
(easy to remove if necessary).

heatinghelp819

Thanks Jughne! Brass plays well with copper and black pipe?

JUGHNE

IMO, for boilers and such, not necessarily for domestic fresh water.

STEVEusaPA

Brass plays well with pretty much all other metals and is frequently used with in place of dielectric unions to avoid electrolysis and corrosion from dissimilar metals.

EBEBRATT-Ed

JMHO, replace it all with steel. If done right it will last a long time

heatinghelp819

Does anything special need to be done when mixing steel and cast iron (is black pipe cast iron??)? Ie where steel pipes go into cast iron fittings...?

ethicalpaul

Nope, they don't hate each other, iron and steel

Joke answer: Yes, if you connect them, they will rust

to answer your imbedded question: Black pipe is steel. Fittings are malleable iron or cast iron. The cast iron ones are thicker and brittler. I have mixed on my system because I re-used a bunch of ancient cast iron fittings. Some installers buy new cast iron fittings I guess.

nicholas bonham-carter

Is the nipple going into the boiler leaking badly, or just weeping?
The Plummer can just crack one of the fittings-the elbow, and with a Union, replace the nipple, and the elbow with iron pipe, and call it a day.—NBC

New England SteamWorks

I would only replace with black pipe. Not that difficult. It's likely corroding because there has long been a very slight leak there.