Malleable iron vs Black pipe

scatgo · September 4

Are the compatible? Working on a 100-year-old heating system. I am going to go from old cast iron to black pipe if it will work. After that copper to the new furnace.

pecmsg · September 4

Copper to the new "Furnace"?

Jamie Hall · September 4

In response to the question — yes they are compatible. "Black iron" is a sort of vague term, really, but at worst it might be steel. So there is no problem mixing and matching there.

Now "furnace" is a word we use for … furnaces. Which are hot air. If you are working with pipe, it's a boiler or just possibly a water heater.

The concern there is whether this is not water or steam. If it is not water, copper is permissible. If it is steam, we very much advise against it, at least above the water line.

GW · September 5

the pipe is generally referred to as steel. Since the beginning

but the fittings either go by black malleable or cast-iron. Two different animals.

yes, interchangeable in heating. The steam purists use cast-iron fittings in general. But I’ve noticed over the year some of the purists are switching to malleable. I’m still stuck in the past, I’m doing all the steam boilers with cast-iron still: but it’s such a pain at times, we are trying to wrench things in a hurry, the wrench doesn’t bite the cast-iron nearly as well as it does malleable.

not allowed to use cast-iron for gas piping. If the starts to settle during a fire, you don’t want fittings popping here and there.

GGross · September 8

Yeah most of the heating pipes that customers in my area refer to as "iron" is actually a carbon steel. its never been worth correcting before, maybe some of the really old stuff is cast iron but it all looks like malleable steel to me. people still refer to sch40 black pipe as iron, its not, it's carbon steel but oh well!

GW · September 8

I agree, I don't have energy to correct the language every time I hear an inaccurate term

EBEBRATT-Ed · September 8

It may be because in the old days there was wrought iron pipe kicking around. But never CI threaded for heating (except for the fittings) AFAIK

"Wrought iron is no longer manufactured on a commercial scale because the invention of cheap, mass-producible mild steel made the labor-intensive production process obsolete."

"

"You cannot buy true new wrought iron because large-scale commercial production ended globally by the mid-1970s due to the high cost of manual labor"

Wikipedia

Malleable iron vs Black pipe

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